Hi Joe.
This usually happens if you have configured one of the hooks (either Live or Test) using wrong mode on your Stripe Dashboard. Go here https://dashboard.stripe.com/account/webhooks and click this thingy to switch data view from Test to Live mode and vice versa:
Then ensure your have Live URL set in Live mode (e.g. https://www.example.com/?asp_hook=live) and Test hook URL set in Test mode (https://www.example.com/?asp_hook=test).