Same thing. I have set a test user for my app. I've verified that the subscription should renew every 5min. Then add this user to my iPad as a Sandbox account in App store for my local development tests. I made a subscription through the app and the renewal is set to 1 day and I am not able to cancel getting the same error: Your request is temporarily unable to be processed. Please try again later.. I've tried to clear purchase history for that account from the Users and Access option for test users from AppStore Connect but this didn't helped at all. And finally - when I try to get purchase history of the test user I get all the sort of information but the transaction receipt is empty for some reason, so I assume then something went wrong with the creation of the subscription on the first place (nevertheless I got message the subscription was successful).

The problem for me turned out that for testing I wasn't using a test account from Settings -> AppStore but my actual account. The way I sorted that out was to LouOut from my iPad and then to log in again. The subscription seems to be living only on the iPad as I wasn't able to find in online in the icloud, or on any other of my devices. For testing now I only use test users created from appStoreConnect -> Users -> Test users and add them as test user in your device.

The problem for me turned out that for testing I wasn't using a test account from Settings -> AppStore but my actual account. The way I sorted that out was to LouOut from my iPad and then to log in again. The subscription seems to be living only on the iPad as I wasn't able to find in online in the icloud, or on any other of my devices. For testing now I only use test users created from appStoreConnect -> Users -> Test users and add them as test user in your device.