One of the reasons we made OmniDazzle a free product is because it had a passionate community of customers, even if that community wasn’t large enough to support a commercial product. Some users with older Macs are still able to get some use from it, which is why we haven’t pulled the download completely from our site.
However, the app doesn’t work as well on hardware or OS revisions that have been released in the last several years (and we have no plans to update the app for compatibility). If you have a MacBook with both discrete and onboard graphics, it’s possible (but not guaranteed) that disabling Automatic Graphics Switching in System Preferences > Energy Saver may cause OmniDazzle to start working. If it doesn’t, we’re very sorry but we don’t have any other fixes or workarounds we can suggest.