"The product distribution file could not be verified. It may be damaged or was not signed."

I have had this problem with two different computers – a laptop and a desktop – and three different networks in the last month, and several different pieces of software. I tried deleting the cache, booting in safe mode, updating everything, and using terminal mode to do something I found on a Google search that I now forget. None of those solutions worked initially but eventually the problem went away. I don’t know why, but I was grateful. I didn’t post back to say “this worked for me” because honestly nothing did, but then something did, but I don’t know what, and I didn’t think that was going to be very helpful to anybody else :-) Thanks for your help.