The sign-in code didn't arrive
Delivery, expiry, and addresses that are refused.
Why: It is usually filtering. Codes come from noreply@tabruns.com.
Fix: Check spam and any filtered inbox, and allow that sender. Then request a new code.
Why: A code was issued moments ago; a second request is held off briefly.
Fix: Use the code already sent. It is valid for 10 minutes.
Why: A wrong or stale code. Each new code invalidates the one before it.
Fix: Use the most recent email, and note there is a limit on attempts before a fresh code is needed.
Why: The domain is a throwaway-mail provider.
Fix: Use an address you will still hold next time you sign in.
Why: You do not need one.
Fix: Close the sign-in page. The free plan works without an account — see Signing in, and what an account is for.