In H9 Control if you click on Settings in the bottom right hand corner of the screen and go to the Eventide Account section, you can change the password that H9 Control has stored for you. If you changed your password on Eventide's website for example, then H9 Control will have the wrong password stored for you.
With regards to buying individual algorithms, we know it's a bit of a pain, but if you ever sell your H9 Max, those algorithms you bought still stay in your account, and if you were to buy another H9 later, you'll have those algorithms on your new H9. And this is why we don't have a one click upgrade option.