I got Capture 2 to work in Mojave. I started over - and reinstalled Mojave on my MacBook Pro, by erasing the disk and reinstalling the OS. Then I installed Capture 2, and it works just fine, thank you.
When I upgraded from High Sierra to Mojave, I had all my USB cables connected to my music devices. This is not very wise - PreSonus recommends that you disconnect all external devices before upgrading OSX. I had tried uninstalling Capture 2, using the procedure recommended by PreSonus, and then reinstalling it, but that did not work.
So, in my case, I decided to erase the hard drive and start over. This was not too difficult because the laptop is fairly new and I did not have tons of applications installed.