failed to connect doorbell after years of no problem

I have a doorbell running for a very long time with no problems. Nothing changed at my home, suddenly I connection to my doorbell become very slowly while connecting to my camera in the backyard works well. So I reset the doorbell and installed also the app again. since then I cannot connect to the doorbell at all. I can see it in my app, etc. the doorbell is very close to my wifi and has excellent connectivity.