In-App Purchases: Receipt Validation Tutorial | raywenderlich.com

I came across the same issue. I solved this by adding the correct paths to the following properties under → Build Settings

Library Search Paths - $(PROJECT_DIR)/OpenSSL/lib
Header Search Paths - $(SRCROOT)/OpenSSL/include

Make sure the OpenSSL project is in the correct location that reflects the above.

@markhmwong Thank you for sharing your solution - much appreciated! :]

This tutorial is more than six months old so questions are no longer supported at the moment for it. Thank you!