Google Nest Cam will not connect

I have tried every way possible but I cannot get it to connect. I have a second nest cam that works perfectly. The next cam with the problem is fairly close to my router. I have done a factory reset and still nothing. The set up process goes well until the final phase and it just then says that it "encountered a problem". The camera worked well for over a year until one day it stopped connecting. All effort to reconnect have failed. :-(