"That email and password do not match an account."
One message covers both a wrong password and an address that never registered. Naming which it was would turn the form into a way of finding out who has an account. Check the address for a typo first, then use Forgot your password? beside the password field.
The reset link
It goes only to an address that has an account, works once, and expires. If nothing arrives after a minute or two, check spam, then try the other address you might have signed up with. The screen never says whether an address is registered, so a silent inbox on its own proves nothing.
"Too many sign-in attempts."
Five wrong tries in a row pauses the form, and the message names the wait. Nothing is locked and nothing is reported — it is a delay, not a penalty.
You signed up with Google or Microsoft
Then there is no password to reset, and resetting one will not help. Use the same provider button you signed up with. Once you are in, Settings → Set a password gives you a second way in for a borrowed computer where your provider is out of reach.
The passkey device is gone
A passkey lives on its device only. It cannot be recovered, copied or moved. Sign in with your password or your provider, open Sign-in and security, remove the passkey that went with the device, and add one on the device you use now.
Your account is scheduled for deletion
An account inside its thirty-day grace period cannot be found by a password or a passkey. Signing in with Google or Microsoft brings it back. If neither is connected, message us before the thirty days are out.
Nothing here works
Message us on the Facebook page with your support reference — the eight characters in the account menu and in the help drawer. If you cannot get in far enough to copy it, the address you signed up with is enough to start. We answer Monday to Friday, 8:00 AM to 5:00 PM, with no promised response time. Never send us your password.