Hi again @dlafreniere
I experienced something similar with connecting Stelpro Maestro Zigbee Thermostat (Thread here) and was later fixed, was an issue with smartthings dealing with longnames in its code.
But in recent days, on my Sinope TH1400ZB thermostat, I see the connectivity icon blinking as opposed to being displayed solid like before - I am not sure what te blinking state means, it is usually displayed as solid or nothing at all - are you experiencing the same behaviour ?