(The thread you posted to was about a similar problem caused by CrowdStrike security software. This is different, so I've moved this to a new thread.)

Is this an institutional computer? Is there any non-standard security software on the system or policy restrictions on the Word installation?

Zotero 6.0.27 changes the mechanism the Word plugin uses to communicate with Zotero for macOS Sonoma compatibility, so some security software or settings might need to be adjusted to allow the new communication method, and we're trying to figure out what that might be for the people experiencing this.

You can tell your IT department that Zotero 6.0.27 uses curl from VBA to make an HTTP request to the Zotero app at 127.0.0.1:23119, since Sonoma blocks the previous communication method, and ask them whether there’s any security software or policy restrictions that would be blocking that.

We're also testing a new version of the plugin that should restore the previous communication mechanism on non-Sonoma Macs. You can test that by downloading this version of Zotero.dotm, moving it into your Word Startup folder, and restarting Word. Please let us know if that fixes the problem for you. But be aware that this problem will reoccur once you're upgraded to macOS Sonoma, so you will need to work with your IT department to figure out what is breaking the plugin version in 6.0.27.

@SteveHaines: I'm not sure what you're saying here. If you revert to 6.0.26, reinstall the plugin from the Zotero settings, restart Word, and still get this error, it's not the same problem. As I explain above, this is specifically due to a change in the 6.0.27 plugin, which was just recently released. But the "Run-time error '5'" is a fairly generic error that has occurred for a small number of people over the years for various reasons, seemingly due to some sort of restriction or misconfiguration in their Word installation. If this didn't start with 6.0.27 for you and/or reinstalling the 6.0.26 plugin doesn't fix it, you should start a new thread.

@jaywen: Can you test the Zotero.dotm I link to above? That should fix this for pre-Sonoma systems, and if so we’ll make that available in 6.0.28 and Zotero 7. But if you’re affected by this, you’ll need to talk to your IT department before upgrading to Sonoma, since the old method won’t work on Sonoma.

All sorted! The sun is shining! Everything is coming up Millhouse :-). Many many thanks @dstillman