As it's a bank that's probably the case, but you could have a change on the server side from
hash($password) == $storedhash
to hash(substr($password,0,20)) == $storedhash
And you wouldn't get in, with any password (including just putting in the first 20 characters)
Re:I hate password rules
by bananasbandanas on Tuesday November 16, 2021 @04:49PM
(#29246765)
More likely they just updated the password during a successful login.
Worse than that must be the sudden realization that your bank probably saves your password in plain text somewhere.