If you have working application in AppStore with inApp Purchases and your certificate and provision profile was expired. You can try to press "Fix Issue Automatically” in Xcode general setting. BUt if you get the following error message.

"An App ID with identifier 'com.mycompany.myproj' is not available. Please enter a different string."

or

"Code Sign error: No matching provisioning profiles found: None of the valid provisioning profiles allowed the specified capabilities: Features: inAppPurchase.."

The solution of this problem is to  o manually add the provision profile that you have created in https://developer.apple.com/account/ios/certificate/

Goto to iTunes Connect. And Click the User and Roles Icon.

Click the Sandbox Testers tab bar.

Add a new Sandbox Tester Account. Create a new tester testing by using different email than your main apple account and click Save button.

Go to your iPhone and iPad device and select the settings icon, go to Tunes & App Store and select your Apple ID and Click the Sign Out Button.

Now go to your test Apps, and when its prompt to enter your Username and Password, use the new sandbox account.