I am actually interested why a working Ubuntu 18 password, although with user apps/Desktop locked under passphrase, after a relatively long period of non-usage

I am actually interested why a working Ubuntu 18 password, although with user apps/Desktop locked under passphrase, after a relatively long period of non-usage stopped working. It was a sort of simple password and entering it was easy, so probability of multiple incorrect attempts should have been low. Are there some default values of incorrect password attempts/periods of non-usage etc upon installation or anything else?