As per Samsung SmartThings SOP. Please continue using the SmartThings Classic app until further notice. You can find more conversations on this subject from SmartThings employees.
I had the same issue and continued using the classic app, today the classic app stopped working so I was forced to logout and login, then the classic app needed to re-pair with my hub!
Switching to the new app it worked fine but now I’ve lost all of my automation’s! Anyone else in the UK having these issues?