@FaizanKhan255 I also faced this issue. Based on my observation, it occurs in specific regions—for example, in Pakistan, sometimes some of Apple's APIs don’t work properly. Try connecting to a VPN and then fetch the products; in my case, I was able to retrieve products that way. Additionally, under the Developer settings on iPhone where you log into the Sandbox account, I wasn’t able to log in without using a VPN. After connecting to a VPN, all of these issues were resolved.

@jezekilj @App Review I resolved this issue—the problem was with the view hierarchy. If your subscription controller is the root view controller, the purchase process works as expected. However, the issue arises when the subscription controller is presented, and StoreKit 2 attempts to present another view on top of an already presented view, causing it not to appear. To fix this, instead of presenting the subscription controller, push it onto the navigation stack and then initiate the purchase. This should work correctly.

I am encountering an error where, on some devices, the purchase process works fine, but on others, I receive the error: "Unable to complete request," with no additional information. The products are loading correctly, but the error occurs when I attempt to make a purchase. What could be the possible causes for this error, and under what conditions might it occur?

I think it's a bug from Apple. In my case, I deleted the application, restarted my iPhone, and then reinstalled the app from TestFlight. It started working again.

I have answered to this question. Kindly follow this link it might help you https://stackoverflow.com/questions/76849106/an-error-has-occurred-try-again-later-in-app-store-connect