Excel 2016 Add-in Disappearing after each close

I have an add-in that works perfectly well with my personal laptop in Excel 2013, i.e. it remains within my ribbon bar after closing Excel. I have "installed" the add-in on a new laptop with Excel 2016 and am having difficulty figuring out why it doesn't remain after each program close. It stays as visible and checked in the Add-ins menu, however, the actual tab doesn't show up. When I Alt+11, my code doesn't pull up either.

Thoughts and ideas? Thanks! Let me know if you need to see my XML code.

Got to where the add-in is located & right click it, is there a box marked Unblock, if so check it.

I think that did the job. I thought I tried that, but perhaps I accidently overwrote the one I did it for.

You're welcome & thanks for the feedback.