I have this same problem. Can we please get some support on this? This is the only reason why I'm using Start10 instead of the out of the box Win 10 Start Menu.

I can tell you that it is not because of a reboot.  I've rebooted many times - this was a clean install of Win10 Pro.

One thing I should mention is that I tweaked my Win10 privacy settings via W10Privacy via http://www.winprivacy.de/english-home/ but not sure how that would be related to the start menu not showing recently displayed apps.

**EDIT**

It seems that it is displaying system apps like settings, store or Photos (the universal and built in apps) - but not desktop apps.  I've modified the setting Start_TrackProgs with Regedit under the key HK Current User\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced and the DWord value of Start_TrackProgs set to 1 Hex.  This is the equivalent of going into the Personalization settings in Win10, and clicking on Start on the left side and enabling Show Most Used Apps.  I'm not sure why it is limited to Universal Apps and not Desktop Apps but it does not display typical desktop apps like Firefox, VLC, Photoshop, etc..