@sleslieuk: See Troubleshooting Errors in Word Processor Documents. You'll need to follow those steps completely, including providing the requested info if you're still having trouble.

You are not allowed to edit this selection because it is protected.

I'm not sure what this is referring to, but it looks like there's something in your document that Zotero isn't able to edit.

If it works in a new, empty document, you'll need to follow the steps on that page in full. As it says, unless you can completely clear the contents of the document and still reproduce the problem, you can isolate and/or fix the problem by following the last step.