That might not be the only issue, I had to use different packaging settings, because the hybrid mode that works better on the old systems would prevent the notarization to complete. I also used the new linker which had problems on 10.7, although that also seemed like a bug which may be fixed at some point. If it looks like this issue won't be addressed in the near future I'll do testing to try and determine what versions can run the signed and notarized version without problems.For people on older systems where it doesn't work, you can right-click and open the "Pale Moon.app" folder and delete the "_CodeSignature" subfolder in Contents. You might also need to do the same for the "plugin-container.app" folder in Pale Moon's "Contents/MacOS".
Regardless, I am not recommending using these builds unless you are on 11 or later, but they may work on earlier versions.