Comment 5 for bug 1428028

Looks like the immediate problem is caused by the add-ins being built against Mono.Addins 1.0, and it not being available on your Fedora system despite being released in 2012. Pinta gets built against whatever's installed on your system, but since the add-ins are prebuilt on someone else's computer they're built against what they have running. (Debian/Ubuntu has Mono.Addins 1.0, the newest version is 1.2) I'm not sure if there's any easy fixes here.

The other side of it is what happens when they fail to install and/or load properly. This should of course be handled better. I'm not sure if we can fix this in our code alone, or if things also need to be changed in Mono.Addins upstream, since it provides all the installation facilities. Which obviously would be a (somehwat ironic) problem since the direct cause of your issues is an unupdated Mono.Addins.