Ok folk , I might have the easiest fix for this ever.
I was having this same problem. Read this whole thread and tried every suggestion , nothing worked )except the whole 2.5 vs 5. Something or that ever. As that is way over my head. )
So he was my solve. Turns out my wife was going through the list of devices connects to our WiFi. Didn’t recognize the 3d printer and blocked it.
As soon as she unblocked it. It connected right away.
Hope this saves some one some agrivation