Junglecat18

Thanks guys. It is indeed a signature issue. I removed the problematic signature part of the file using Terminal: xattr -r -d com.apple.quarantine <path to file or app> The only problem with this is that if the file in question is going to be harmful you your computer, you have just let it straight in. But as this is an app from the official Affinity site I will happily take that minimal risk to get Publisher working again. Anyway, all fixed!

I have had to reinstall an older Mac OS (Catalina 10.15.7) and with it Publisher (1.10.5). But now, 3 browsers later I am still getting the same message: My Terminal is throwing up this: Last login: Thu Aug 11 09:22:38 on console ga@Graemes-Mac-mini ~ % spctl --assess -vv /Applications/Affinity\ Publisher.app /Applications/Affinity Publisher.app: invalid signature (code or signature have been modified)