Hi Jennyfer,
Thank you for your screencast explaining the issue. Ok, the first issue there is you have an updated version of X 9.0.8, but outdated version of Cornerstone plugin. You can refer for what is the latest versions here. You can simply deactivate and delete the Cornerstone plugin, and X will prompt you to install Cornerstone, please follow that prompt (on top of the admin dashboard) to reinstall the latest version of Cornerstone.
Now after you update Cornerstone, make sure it is validated. Then navigate to Cornerstone > Templates and look for the Design Cloud tab.
Template Manager Documentation
Now, on another note; I see that you already converted your license to PRO, so you should now switch to PRO. If you follow this path, you can disregard updating the Cornerstone and just deactivate it, then install the latest version of PRO 5.0.8 and activate it. If this sounds too complex, for now, you can go on with X.
Installing PRO
Hope this shed some light,
Cheers!