The free offers for Gems are provided by Tapjoy. In order to receive your reward you will need to reach out to Tapjoy for assistance.

You can reach them through the menu button at the top left:
1. Tap Reward Status
2. Tap "Not Rewarded"
3. Select the offer you are having trouble with. Note: You may have to wait a few hours before you are able to contact Tapjoy support
4. When available, tap "Request Support"
5. Input your email and then explain your issue in detail. Don't forget your User ID which can be found right below the "Request Support" button.

Note: Be sure to read the FAQ before proceeding with the contact form, to make sure that you have all of the necessary information for Tapjoy to assist you.