Wifi password says incorrect

I cannot connect any devices to home wifi. I get the message “incorrect password.” I’ve had the same password for many years and it was correct.  Despite this, I used xfinity app to change WiFi password and the new password also gets the same message “incorrect password.” I know the password is correct. I have reset the modem, unplugged it, plugged it back in, etc. I have reset devices. When I go to connect to my home network, it still tells me my password is incorrect. Help!!?