Okay, I realise you are talking about signing into AB. As you managed to get into post this I assume you had used the 'remember me' facility. In case you lose that facility (sometimes I have to sign back in, especially if I fully clear my cache or use a different device) you should follow the AB process for recovering your password.
Might be worth resetting it now and making a note of the new one.
To do this, on the log in screen it says "If you have forgotten your password please Click Here To Reset Your Password."
For that to work though you probably need to still have access to the email account to AB previously