LibreOffice 6.0 won't start

I just installed LibreOffice 6 as I was running 5 and couldn’t get it to install the Zotero integration add-in. Now I can’t open LibreOffice at all - I see the colourful cubes and the logo and then get an error message saying

The application cannot be started.
[context = “user”] caught unexpected
com.sun.star.deployment.DeploymentException: Extension
Manager: failed to read data entry in configuration backend
db:
file:///C:/Users/User/AppData/Roaming/LibreOffice/4/user/un
o_packages/cache/registry/com.sun.star.comp.deployment.co
nfiguration.PackageRegistryBackend/backenddb.xml

I got a similar or possibly identical message when I was running LibreOffice 5 and clicked on ‘Add’ in the extension manager, trying to install Zotero integration. Other steps I have taken so far include making sure I have the latest version of the Java Runtime Environment (I do), installing the Java Development Kit (someone on a forum said this might help install the Zotero extension), and restarting my computer.

Any help would be appreciated…I really don’t want to buy MSOffice but I need a functioning office suite!

Thanks.