Thanks for posting.
From what you've recorded from the Protege console during start up and the fact that you can see the help document in the menu, the Snapshot tab is installed correctly.
From the Project -> Configure menu, you should see a panel like that in the attached picture:
Screen Shot 2017-03-28 at 09.42.09.png
Assuming that you can see "EssentialSnapShotTab" in the list, and that you've checked the "Visible" checkbox, are there any further messages appearing the in Protege console window?
Failing that, you can re-install the Snapshot Tab only by re-running the installer and de-selecting everything except the Snapshot. You will be prompted for a location into which logs of the install will be captured - this is where you installed things like the baseline meta model originally - and it is safe to use that folder again.
Let me know how you get on
Jonathan
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