I login and it just changes it to Signed in with Google.
What happens when you actually click the login button?
Try it in incognito mode.
I get the account selector window and I select my account and then it changes it to Signed in with Google but doesn’t do anything. Incognito didn’t help using another browser didn’t help (I’ve tried three total).
That happened to me too. Wait for a little bit more. This happens because, Thunkable website sometimes doesn’t redirect user immediately.