Happening to me too. The issue is similar to what has been reported countless times.
Scenario to help further debugging (if they even care to read this thread…)
1 - My subscription ended on March 24.
2 - There was a problem (renewal unsuccessful) but I didn’t received any email regarding any issue or pending invoices so I was not aware.
3 - On March 29 I’ve noticed the downgrade to the Free Tier and discovered the billing problem.
4 - On March 29 I’ve clicked on the pending invoice and paid it.
5 - Today we are at 1 Apr and It’s still showing as Free. The money was already transferred, as seen in my online banking.
This is clearly a bug with the billing system, and the worst thing is the complete lack of response by the support team. I have never faced such a crude problem with billing with any other product. It’s an horrible feeling - to pay and don’t receive the product. And the complete lack of response from the support team is just icing on the cake.