You can try restarting the computer. Sometimes that fixes this.  If not then…..

Actually, it is “Universal Plugin Installer Agent”, not “Unified Extensibility Platform”.  That is what the OS is supposed to use automatically when you try open it.

If you right click and don’t see “Universal Plugin Installer Agent” then Creative Cloud would probably need to be reinstalled or repaired to be able to install from a CCX file. Adobe could maybe fix Creative Cloud for you without reinstalling it.

You can also install manually which will bypass creative cloud., Here is a link to download the manual installer. There are instructions on the page.

Manual Plugin Installation