I usually stay logged-in, so I logged out to log-in back again and it worked. (Except that it made me realize that my password manager mismatch and use my Renoise backstage account instead, but that’s another issue 
)
Guess it happened only because your password was too small and they changed the rules, but I agree with you, it feels weird to have such an action happening without giving you any notice (either beforehand, or at least a notification explaining what happened)