Hi @muz 
Without any backtrace or console errors, it will be a little difficult to identify the culprit. Are you using a wild card value ‘*’ for your Access-Control-Allow-Origin using the rack cors gem? If that’s the case it might be conflicting with the forest_liana configuration.
My best guess is this is the issue. Another user has encountered it previously and it has been solved by the tech team on this community thread. You can also take a look at this section in the docs to configure your CORS headers.
Feel free to send our way any error from the backtraces/or browser console logs so we can get to the bottom of this for you.
Cheers,