I can no longer open my account on my Ipad. it takes my username Clauser1960 as used by someone else. I have changed the password without any result.

I receive notifications, but I can no longer log on my Ipad. It takes my username Clauser1960 as used by someone else. I have changed the password with no results, because it treats my account as a new one without my username. It is weird, since I receive notifications on my cellphone and on Gmail al clauser1961@gmail.com. Please help me to find a solution.