Thanks Michael. That's fixed it nicely. Apologies for the delay in replying, one of my disks decided it was time to retire.
For the record:
- Download the zip file from the link Michael provided.
- In a scratch directory, expand it.
- Go to
conf/lib and move the
refnotes directory somewhere else.¹
- Move the expanded zip here, changing the name to
chown -R apache:apache refnotes²
- If you disabled the plugin in the extension manager, reenable it.
¹If you simply rename it to something like
refnotes.new, then the extension manager gets confused.
²Or whatever username your browser runs under.