Trouble installing EWQLSO

In 2014 I downloaded East West. I unzipped, and installed without a problem. Now I need to install once again on my iMac (El Capitan). But when I run the installer it's not possible to install it on my drive. I get this exclamation mark on the main drive telling me it's not possible to install. What am I doing wrong. Why can't I install it?

I moved the unzipped folders to my iMac, instead of downloading the zipped file. Don't think that causes the problem.

I have had EWQLSO for some time, used it occasionally. I think you have to go through the whole installation process from scratch. I switch drives, some time ago, and I seem to remember that. But I'd contact their tech support to verify that.