Why does Ecobee Integration app keep losing its authentication in Hubitat?

Respectfully, the native Hubitat support for Ecobee is not very robust, and it does not recover from many failure modes exhibited by the Ecobee API Servers.

If you are interested, you may wish to try my Ecobee Suite, which is far more reliable and offers many, many more features and capabilities. It is free, and you can in fact use it alongside the native support to see if it handles things better for you (or not). You can learn more about my Ecobee Suite by clicking here.

FWIW, I have offered to help the Hubitat staff make their Ecobee support more robust, and the offer still stands.