For me, I was testing this on my own device. You have to do two things:
1.) Log out of the Sandbox in Settings -> Developer -> Sandbox on the device after you clear purchase history
2.) Make sure your personal account is logged out in Settings -> Apple Account -> Media & purchases
Now you'll get fresh subscriptions as they are not somehow sandboxed into your own account
Topic:
App & System Services
SubTopic:
StoreKit
Tags: