Bambu P1S “Invalid Password” on Google Mesh – NOT a Bad AP Board

Bambu Lab P Series Troubleshooting
1

I wanted to document this in case it saves another P1S owner a lot of troubleshooting or an unnecessary AP board replacement.

My Bambu Lab P1S suddenly would not connect to my home Wi-Fi. My setup is Optimum internet with a Google Mesh/Google WiFi network using a combined 2.4/5 GHz SSID.

Symptoms

The P1S would:

  • See my Wi-Fi network.
  • Report “Invalid password” in Bambu Handy even though the password was 100% correct.
  • Show the correct SSID on the printer after some manual configuration attempts, but its IP remained 0.0.0.0.
  • Fail on both my normal Google WiFi network and Google Guest network.
  • Eventually have Bluetooth disconnect during some Bambu Handy setup attempts.

Bambu Lab support suspected a bad AP board and recommended replacing it.
Before doing that, I kept troubleshooting.

Things I tried that DID NOT fix it

  • Rebooting/resetting the P1S.
  • Forgetting/re-adding Wi-Fi.
  • Bambu Handy setup multiple times.
  • Google Guest Wi-Fi.
  • Confirming WPA2 and 2.4 GHz were available.
  • Moving the P1S closer to the Google router.
  • Disconnecting an aftermarket lighting kit.
  • Using user_wifi.cfg on the SD card.
  • Creating a 2.4 GHz WPA2 Windows Mobile Hotspot.
  • Downgrading the P1S firmware.

The Windows hotspot was especially interesting because it was definitely 2.4 GHz, WPA2-Personal, 802.11n, yet the P1S still reported an incorrect password.

The test that changed everything

I tried my iPhone Personal Hotspot with “Maximize Compatibility” enabled.
The P1S connected immediately and received a real IP address.
I was also able to bind the printer to my Bambu account, communicate with it through Bambu Handy, toggle the light, etc.
Even more importantly, I changed the iPhone hotspot password to the exact same password I’d used on the Windows hotspot.
The P1S still connected successfully.
That proved the password itself wasn’t the problem and strongly suggested the P1S Wi-Fi hardware/AP board was capable of working.

The eventual fix

I bought a NETGEAR EX6110 AC1200 WiFi Range Extender for about $40.
I manually configured it instead of using WPS.
The EX6110 connects upstream to my Google Mesh on 2.4 GHz, but broadcasts a separate network specifically for the P1S:

SSID: BambuWifi
Band: 2.4 GHz only
Radio: 802.11n
Security: WPA2-PSK / WPA2-Personal
Encryption: AES/CCMP
5 GHz: Disabled

I used the same Wi-Fi password that had successfully worked with the iPhone hotspot.
Before connecting the printer, I verified the new network from Windows Command Prompt using:

netsh wlan show interfaces

It showed:

SSID: BambuWifi**
Band:** 2.4 GHz**
Radio type:** 802.11n**
Authentication:** WPA2-Personal**
Cipher:** CCMP

Result: SUCCESS

The P1S connected to BambuWifi immediately and, instead of 0.0.0.0, received a real 192.168.86.x IP address from my home network.

My phone and computer remain connected normally to the original Google Mesh network.

I tested:

  • Bambu Handy detecting the P1S while my phone was on the normal home Wi-Fi — works
  • Controlling the P1S through Handy — works
  • Bambu Studio on my Windows PC while the PC was on the normal home Wi-Fi — works
  • Sending an actual print from Bambu Studio → P1S — works and the printer started printing

The final setup is essentially:

Google Mesh → 2.4 GHz → NETGEAR EX6110 → dedicated 2.4 GHz WPA2/AES network → P1S

Everything else in the house stays connected to the normal Google Mesh network.

Takeaway

If your P1S suddenly gives you “Invalid Password”, refuses to obtain an IP address and sits at 0.0.0.0, especially with Google/Nest WiFi or another mesh system, don’t immediately assume the AP board is dead.

Try connecting the P1S to a completely different 2.4-GHz network first. An iPhone hotspot with Maximize Compatibility enabled was the critical diagnostic test in my case.

If it connects to the hotspot and receives an IP, your Wi-Fi hardware is at least capable of functioning.

A cheap extender/access point broadcasting a dedicated 2.4 GHz, WPA2-AES, 802.11n network may solve the problem.

Obviously, this doesn’t mean every P1S with these symptoms has the same issue or that AP boards can’t fail. But in my case, Bambu support’s recommendation to replace the AP board would not have addressed the Wi-Fi compatibility issue we ultimately isolated.

Hopefully this saves somebody else a few hours and an unnecessary part replacement.

2

But the question is why?

Printer suddenly stopped connecting, and this remained after resetting the printer. But printer would connect to a new network. At that point I would suspect the wifi router.

So you worked around this by purchasing a wifi extender and connecting to that. It might have been an option to reset the router as well, rather than purchase an extender. However given the hassle of reprogramming a wi-fi network, I might have bought a US $40 extender as well.

If you move to a VPN later with a killswitch, you may have an issue with the extender creating a separate network. That however is not a factor right now.

Anyway congrats on diagnosing it.

3

And that’s the 10 million dollar question…why?

I probably should have made some of this clearer in the original post.

The Google Mesh wasn’t new to my network environment. The P1S had been connected to this same Google Mesh system and working normally for over a year before this suddenly started happening. There wasn’t a new router or network change that immediately preceded the problem, which is part of why I initially didn’t suspect the Google system.

I did restart the entire Google Mesh network during troubleshooting, including testing with only the primary Google router powered on and the mesh points disconnected. The P1S still gave the same invalid-password error.

One complication with Google Mesh is that it combines the 2.4 GHz and 5 GHz bands under the same SSID and doesn’t give you the normal option to split them into separate networks. The P1S only uses 2.4 GHz, so I couldn’t simply create a dedicated 2.4 GHz SSID on the Google system and test it that way.

What really threw me was that I also created a completely separate 2.4 GHz WPA2 hotspot from my Windows PC and the P1S rejected that with the same “invalid password” message. The iPhone hotspot with Maximize Compatibility enabled was the only network it would initially join.

The extender was basically my attempt to reproduce a simpler/legacy 2.4 GHz Wi-Fi environment permanently. The EX6110 connects upstream to the Google Mesh on 2.4 GHz but gives the P1S its own dedicated 2.4 GHz 802.11n/WPA2-AES SSID. Interestingly, the P1S still receives a 192.168.86.x address from the Google network, and devices connected to my normal Google SSID can communicate with it, so the extender isn’t creating a separate routed LAN.

The “why” is still the part I can’t completely answer. The P1S worked directly on this Google Mesh for over a year and then suddenly stopped authenticating to it. Something about the way the P1S was interacting directly with the Google Wi-Fi (and, oddly, my Windows hotspot) was causing authentication to fail, while the iPhone compatibility hotspot and EX6110 work fine.

The main reason I wanted to document all of this was that Bambu had diagnosed it as a bad AP board. Once the printer successfully joined the iPhone hotspot, received a real IP, reached Bambu Cloud, responded to commands through Handy, and even completed a firmware downgrade, a failed AP board no longer seemed like a convincing explanation.

I’m not claiming the extender is the universal fix for this error, and I’d still love to understand exactly what changed after more than a year of the P1S working on the Google Mesh. But hopefully the hotspot test and dedicated 2.4 GHz network give someone else a couple more things to try before replacing hardware.

4

I would suspect a “stealth update” to the router from Google.