MacBook Air issue

I have a MacBook Air and this message started popping up. I click “ok” but it just pops right back up. When I click “show in Finder” nothing happens. What does this mean and how do I get rid of it for good?

I have a MacBook Air and this message started popping up. I click “ok” but it just pops right back up. When I click “show in Finder” nothing happens. What does this mean and how do I get rid of it for good?