I cannot sign in

Go through these in order. The first two account for most cases.

1. The address

You sign in with your email address, not a username. If you have more than one address, try the others: people routinely register with a work address and then try to sign in with a personal one. Check for a stray space at the start or end, which phone keyboards add generously.

2. The password

Check caps lock. Type it into a plain text field first to see it, then copy it across. If you are unsure, do not keep guessing — three wrong attempts locks the address out for 20 minutes. Use Forgot password instead, which is faster than the lockout.

3. Is it telling you that you are locked out?

Then that is the answer, and the page shows how long is left. See being locked out.

4. The reset email has not arrived

Check spam. Wait two minutes. Resets are limited to three requests a minute, so requesting it repeatedly does nothing useful. If nothing has arrived after ten minutes, the address you typed is probably not the one on the account — try the others.

5. The two factor code is rejected

Almost always a clock problem on the phone. Turn on automatic time setting and try again. Failing that, use a backup code. See losing your two factor device.

6. It signs in and immediately signs out

Something is discarding the session. Check that cookies are not blocked for this site, turn off any extension that clears storage, and try a normal window rather than a private one. If it only happens in one browser, it is that browser.

7. The account may be suspended

Rare, and it says so when it happens. See suspended accounts.

If none of that helps

Write to support from the address you believe is on the account, and say what you see on screen word for word. If you have an armed vault with a deadline coming up, say that in the first line, because the clock does not stop while this is sorted out.