I often have to enter my password several times before I am allowed to log into AGOL/arcgis.com. VERY BUGGY.
I have the password saved in Chrome. I go to arcgis.com to log in. It has my username/pswd already populated in the fields. I press "Sign In", and I get rejected. I don't make any changes, and press "Sign In" again after being denied. It magically works the second time.