Yesterday I upgraded Hacs to 2.0 and didn’t like it so I restored a full backup of home assistant. This of course broke the Smartthings integration. I went into the Smartthings mobile app on my Samsung phone to reauthorize home assistant and got this error message:
I tried again on an iPhone and it seems to have worked. One thing that the iPhone SmartThings app requested was permission to access devices on my local network. I think this may have been what was required to reauthorize the connection with home assistant.
Just documenting this for my own future troubleshooting and hope it may help anybody else that runs into this issue.