Did you ever think it might be a good idea to contact your broker and ask
Did you think perhaps that because the account has not been used in 4 years, it would have gone into a "Dormant" or "suspended" state
Did you think that if you perhaps asked your broker what happened, that they may be able to re-activate the account ?
it's highly possible that you are getting this message because the I.T. Guys have suspended your login because they want you to call them and tell them why you have not logged in for such a long time
Contact your Broker, we can't help you.
i would have assumed that this would be obvious
Why are you here ?
if i forget my facebook login, i don't go to twitter and ask why i can't login
i contact facebook