PM Self-Serve and PM Community are different accounts with different logins. (Though they do need to have the same email address if you want Community Rewards/Points linked to your service account.)
Many PM subscribers don't have Community accounts - it's not required.
And many Community members don't have PM service accounts - they could be former subscribers who moved to other providers, they could be any random spammer or stray from anywhere on the internet.
If your phone service worked until it stopped working on the next billing cycle then it's almost always because no payment was made (or no payment was accepted). AutoPay sometimes breaks because it's somehow misconfigured (on one end or the other). Payment vouchers don't deposit themselves into Available Funds balance unless the PINs are properly submitted.
The usual advice for browsers - clear cache and cookies, disable scriptblockers and adblockers - will correct the vast majority of user-side errors during Self-Serve sessions, especially if one browser is used to access multiple Self-Serve/Community accounts.
