This is caused by:
1. You are trying to add the tab to a personal timeline or using an app that is not published/verified
2. You are using shared SSL
- Make sure you are on the latest version of Social Commerce.
- To update, download the latest version from the oboxthemes.com website under Dashboard > My Plugins and reinstall it.
- Go to in your WordPress admin menu and ensure no SSL errors appear in Step 2 and re-add your page tab.