Strange Problem with MS Power Point

I have a Power Point presentation that works differently on two Macs even though each Mac runs the same Mac OS and the same version of power point.

Let me explain -

On a Mac Mini 2012 running OS 10.11.6 and MS Office 2011, after I launch the PPT presentation and select view>slideshow, the slide opens full screen on the monitor the way it should.

If I do the same thing on a MacBook pro 2011 running OS 10.11.5 and MS Office 2011, after I launch the PPT presentation and select view>slideshow, the slide doesn't really change - the toolbar is still there and all that happens is that the desktop icons disappear.
I expected the slide to open full screen like on the Mini.

The presentation itself is on a USB flash drive so it is identical in both cases.

I just reinstalled Office 2011 on the MacBook pro, but the problem is the same.
To reinstall, I moved the existing Microsoft folder from the application folder to the trash - are there other MS files I should have trashed as well before installing MS Office again?
Or does anyone have an idea what might be going on?

Thanks.

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