Chrome Extension Subscription: Code to check for License

Hi, we need an expert chrome extension developer who know about subscription flow. We have an extension that is set to be paid with monthly subscription, so, we need a code snippet that checks if the subscription is expires, else it should redirect user to the extension page. We're using Google Pay for the payments. We already have a developer that created the extension and he is stuck with subscription flow. so, just need the sample working code. Thank you! budget is $15 AUD