“Creative Cloud Installer” is damaged and can’t be opened. You should eject the disk image.

I've been getting this prompt for months and it is driving me crazy. My main computer doesn't have an issue, but I have a Mac that stores all my movies, photos, etc. It isn't touched often, but every now and then I need it, and every now and then I need an Adobe app. (that's how this probably has lasted so long - I usually get tired of trying to find a solution).

I've already been trying to resolve this for over an hour today. Talking with the painfully slow Adobe chat, searching the net, trying things. Nothing is working.

It doesn't matter which Adobe app I download, this is the prompt I get when trying to install:

“Creative Cloud Installer” is damaged and can’t be opened. You should eject the disk image.

Please help.

Mac OS X 10.11.6