Hey archanathiruvoth,
It sounds like you're having trouble making an in-app purchase.
According to Buy additional app features with in-app purchases and subscriptions - Apple Support, if you're having trouble making an in-app purchase, make sure that your payment information is up to date. Here's how to do that: Change, add, or remove Apple ID payment methods - Apple Support.
If it appears the purchase went through, but the in-app purchase isn't displaying then these steps might help: If an app unexpectedly quits, stops responding, or won’t open.
If you're still unable to get the in-app purchase, report the problem using these steps: Report a Problem - Apple Support
Cheers.