Stick Up Cam Battery Won't Re-connect to WIFI

I have 2 stick up battery cameras on the same WIFI network. They have been working fine for weeks . Yesterday one of them reported that it was not connected to WiFi. I eventually tried to set it up again. I followed the procedures and got as far as “Rome wasn’t built in a day”. It then said that the WIFI password had been entered incorrectly It hadn’t, I was reading it from the back of the router and both my wife and I tried several times with the same result. The camera was within feet of the router, the battery is 100% and I definitely haven’t changed the WIFI password. (All other devices are connected as normal, including the other camera). Could it be a fault in the unit?