There are limits on webhook subscriptions, but it starts at 10,000 subscriptions per Client ID, and a max of 3 subscriptions to the same topic, so I don’t think that’s an issue.
Your first point of call should be to check the Get Webhook Subscriptions endpoint, this’ll let you easily see if the subscription is active. If it isn’t then the issue is with creating the subscription, if it exists and you’re not getting notifications you know you should for that topic then the issue is like with your POST handler. I believe there are some certain circumstances where a it can appear that a subscription is created without errors but actually doesn’t get created, so that endpoint is the best way to check.
Also, refreshing subscriptions daily when there’s a 10 day lease is a tiny bit excessive. Resubscribing early is fine, but when you’re only a 10th of the way through your current lease there’s no real need for that, especially since the endpoint exists to check if a subscription is still active or has died somehow.