Honeywell thermostat pro series 6 does not connect to xfinity wifi

My honeywell thermostat does not connect to xfinity wifi anymore.

It was working for last 2 years without any issues, but recently from few weeks it stopped connecting.

Everytime I try to connect the thermostat to the wifi it says "Unable to connect to the wifi, incorrect password".

I tried the following and none of them worked, same error "Incorrect password"

Reset wifi password 

Reset thermostat settings

Split wifi band, 2.4 Ghz and 5 Ghz

Finally, just to check if it was the router issue, i tried connecting the thermostat to my mobile Hotspot - it got connected instantaneously 

So the issue seems to be in the xfinity wifi/router. 

Please let me know how i can get this issue resolved?

Thanks,

Supritha