Elements not appearing on Elements Tab

Sometimes it might cause for old transients.

You can try to install and run Transient Cleaner (https://en-ca.wordpress.org/plugins/artiss-transient-cleaner/).

1. Install Transient Cleaner
2. Navigate Dashboard -> Tools -> Transients
3. Set Clear Expired Transients -> Enable
4. Set Clear Expired Transients -> Clean Now
5. Set Remove All Transients -> Enable
6. Set Remove All Transients -> Optimize Afterwards
7. Set Remove All Transients -> Clean Now
8. Save Changes
9. Recheck your Cornerstone for functionality