I'm having the same issue. I linked my home internet service with my mobile to bundle them together for the discount. Ever since doing this I have been unable to access the my account page. Everything else I can log into fine.
When the password gets reset, I type it in and it prompts me at the same page with red text saying immediate password change required. When I try to change the password it says incorrect username or password. I've spent over a week trying to fix this issue now and all the troubleshooting steps get you nowhere.
That's strange because Yes Crowd and MyAccount should have the same login details.
You'll need to click on that Message Us link so they can obtain your details and look into what the issue is.