There are two situations it may be asked to pay again even if you have purchased.
If X-VPN status is shown as free after you purchased the subscription, It’s probably network issues that lead to your subscription failing. You need to refresh your purchase status manually.
1. Confirm that the account you are logged into the app store is the account you used to subscribe.
2. Try to restore purchase.
Your subscription is only for mobile, and you are using it on PC now.
After you run out of the free data we gifted on PC X-VPN version, you need to have a ForAllPlatform subscription to use on PC.