Thank you Riley_S for your response. No VPN is in use. That being said,today, after over a month with the error message,the app started working normally without me doing anything. Maybe a server side...

December 2nd Kasa app still reports "Network unstable" I cleared the catche and deleted the app data. Then I uninstalled the Kasa app,and restarted my phone. I then re-installed the kasa app and...