Password for both account and store allows sign-in: Try it in Support and totally fails all and every time. Even changed password to be allowed-in; once, used new password to sign-in to account; but failed to sign-in to support continuously?
You'll want to make sure this isn't being caused by the web browser possibly caching an incorrect password. Please try the following and then see if you can log into the support site.
Clear the cache, delete any cookies, and restart the web browser.
Statement brevity contains inductive information: Password works; but not for Support. So can deduce the password contains characters allowed by both Account and Store but not Support.
As the password works in browsers for both Account and Store eliminates the trite excuses of bullets 1 to 4.
The password for logging into support is restricted to 20 characters. If the password you've set is longer then that it could be the reason it's failing. If that is the case, please reset the password again to something shorter.