Thermostat not recognized by network

Thermostat went offline. I deleted it and reinstalled. However, it still is not recognized by network even though the thermostat is working at the site. How to get the network to recognize it. It went offline without warning.

How strong is the wifi at tstat location?

very strong. Exclamation point showing next to wifi indicator

Had a very similar issue. See the link and the other embedded link. Recommend you go to your router and Release and Renew all DHCP devices. That fixed it for me. Going offline issue occurred again, but I think that is a different bug than not being able to connect to the Internet with the Thermostat and the Offline Icon.