now you are scaring me 😟 We had help from an accountant for the first extension (based on non-O retirement visa) last year just to save time, but we had all the necessary docs and met the requirements we could open bank account and immediately transferred the required 800k from our foreign account, we had to make a CoR, pictures of house, map showing where we live and went to the bank ourselves to collect statememt and letter. The agency just saved us a lot of time by collecting all our docs and passport and went to IO and 2 days later we had our EoS mult. entry. After several months we now know exactly what it needs and now we have more time to prepare. We will try next extension ourselves, why shouldn‘t this work for us without an agent?
Then just try to register again, if it says "mail already registered" then just take another mail. Even you can register and make an account if you want. I just did it two weeks ago, because my landlady asked me to make my own TM30s so she doesn't need to do it all the time.