I got my subscriptions all working in the sandbox about 5 days ago, but a day after I finished testing it I started getting 500 server errors every time I try to test my subscriptions in sandbox and in production. I have not changed the code what so ever and my JWTs still decode perfectly.

Any ideas why this is happening? I've contacted Google many times but most of the people I get a hold of clearly have no idea what they are talking about... Has anyone ever run into this issue before? Any input is appreciated!
The failing red line is the google sandbox code:
<script src="https://sandbox.google.com/checkout/inapp/lib/buy.js"></script>
POST:
[,"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.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.sju0xaOf9u3ufxow0XxWF4j-QUY0XgtF0A0d8g1rRiQ",,,1]
Response:
[,,4,"VTTMKJ"]