subscription receipt not received after reinstall app

Question

I am implement renewing subscription in my application.

When I purchase pack then I get receipt from app store by following code

NSURL *receiptURL = [[NSBundle mainBundle] appStoreReceiptURL];
NSData *receipt = [NSData dataWithContentsOfURL:receiptURL];

Question : When I reinstall my app. I get nil from receipt In iPhoneX(11.4.1) But working fine in iPod(9.3.5)

Thanks in advance