What does the "Couldn't obtain plugin principle class" message mean?

If you have just upgraded to an Apple Silicon Mac and are getting the following error: “Couldn’t obtain plugin principle class” when opening RapidWeaver, please read the below.

RapidWeaver Classic is a Universal app and compatible with both Intel and Apple Silicon-based Macs.

To take advantage of RapidWeaver on Apple Silicon based Macs, you’ll want to make sure all your plugins are up-to-date. If some of your installed plugins are not Universal, they will not run natively in RapidWeaver on Apple Silicon and you’ll see one of the following errors:

RapidWeaver Failed to load some plugins

PluginName: Couldn't obtain plugin principle class

How to Fix

To make older plugins (that are not Universal) run on an Apple Silicon Mac you’ll need to install Rosetta for macOS.

Apple has a guide on how to install Rosetta. Along with information on how to enable it on a per App basis. Once you have Rosetta installed on your Mac, you can get info on RapidWeaver in the Finder and check the “Open using Rosetta” option under the General settings.

Once this is checked you’ll need to re-launch RapidWeaver and your legacy plugins should now run just fine.

However, by running RapidWeaver under Rosetta, you’ll lose some of the huge speed improvements Apple’s new M class silicon chips can bring. Please check with the developer of any plugins you’re using to see if they are available as Universal builds. If they are not available we’d suggest looking for alternative solutions that can cover the features you’re missing.

Help, I can’t see the “Open using Rosetta” option?

The “Open using Rosetta” option is only visible when you’ve tried to run a non-native app. Plugins won’t trigger the installation of Rosetta, so you’ll have to do this manually. Follow the steps outlined below.

Step 1: Open Terminal (Finder > Apps > Utilities)
Step 2: Paste the following inside the Terminal window that appears:

/usr/sbin/softwareupdate --install-rosetta

Step 3: Press return

That’s it. You should now see the option to “Open using Rosetta” in the RapidWeaver info panel in the Finder.

Here’s a video on YouTube that explains this process in more details.