After upgrading to the latest firmware, no SD card can be read in the card reader. The cards are working and formatted correctly, and the card with all my files and timelapse works ok on Windows. No card can be read or formatted in the reader. Removed the screen and checked the ribbon cables; all ok. Factory reset, no improvement. I’ve logged a ticket, but since the printer is printing just fine, they do not have a significant rush to fix it, as I know they are short-staffed. Just annoying. This is not a card issue but a software/hardware issue with the printer. I’d roll back the firmware if I could. I’ll keep printing via the cloud (or LAN if the cloud is down) until someone comes back to me. Posting in the off-chance someone has had something similar?
Now the screen has died but can I get support to respond. Nope. Short staffed, yeah I get it, but c’mon! Early adopter punishment.
Did you have any updates?
I was told that my SD card was probably the fault and to try another. They didn’t read that I’d tried 5 various sizes and brands and the card that came out worked just fine. The screen is faulty, and now dead. 
not much I can do. I could take the screen apart and see what’s not soldered correctly or what component has failed and fix it myself but I won’t for something this new and with warranty (could be a bad solder joint causing a short).
So I’ve been asked to strip down the FPC cable, to see if it’s a poor connection at either end. Since it’s not an issue at the screen end, looks like I’m going all in. Replacing the FPC cable from the AP board to the LCD display | Bambu Lab Wiki honestly, I’m comfortable with it, but not everyone would be. Not the best service but at least they reply every couple of days 
Update: The issue was not related to firmware but with the board in the screen. Initially, it was a SD-Card fault which eventually led to the screen failing. The backlight functioned intermittently but the screen did not display anything. The problem was resolved by replacing the screen that was shipped to me.
This sound a little bit strange.
Today I have updated to the latest version and run exactly in the same problem you have had.
After the update he told me that there is not enough space on the SD card. But there was more then 2GB free. Video was disabled.
I formatted the card with the printers internal routine and was able to save the log files to the card as a test.
But when I want to print via WLAN mode Bambu Studio told me this is not possible without a SD card.
In the SD card view of Bambu Studio was a notice the the SD card is not compatible (any more).
As I have to X1C printers I replaced the card with the one from the 2nd printer. But still the same error.
As I have ongoing problems with connecting the printer to the cloud I now have no way to print anymore.
I have invested days in trying to get the printer to the cloud and I‘m read hundreds of post about this WLan / Cloud problem. I know all the things that don‘t work like using a WLAN channel of 11-13.
That fu**ing firmware sucks so much!!!
My hope was that it is fixed in the new update and now I have nothing.
I‘m have no ideas to downgrade as the printer is not connected to the cloud.
I cannot find the right words how I hate this firmware.
Mine did the same thing but I can’t print no matter what card i put in it dosent work. Now what?
I have printed several files since update and all the sudden i get an error code that says SD card not found. removed sd card checked with my pc it has a bunch of files on in. My pc can read the card just fine. it just started to print did not make it thru the first layer.
I updated to the latest firmware because it told me I could only print the moon lamp with the new firmware. After update mine also said it could not see the sd card. Replaced it with another but now uploading this model is taking forever. What the hell is wrong with this new firmware???
Welcome to the forum.
Have you formatted the SD card via the printer and power cycled yet?
I removed the original card. Inserted a new card. It worked. Did a reboot but, I never use the sd card, I only print over network. Why do I even need that card?
Unlike the P/A series printers, the X series printers don’t actually need a SD card so you can remove it.