This link:

Powerpoint 2016 and Automator. Can't see ppt in the presentation folder of Automator

https://answers.microsoft.com/en-us/...44ea265?page=2 . . . reports others having the same issue with the missing entry(s).
Read all the posts and you'll see that a poster named LukeBusbridge has kindly copied the necessary files from an earlier PP version and uploaded them to his OneDrive for others to download and use to hopefully 'fix' the missing entries.
It appears to have helped some.