Fully qualified path like in this topic: Will not pull content
So in CMS settings, if would be recommend to have full path there, so for example:
Say your web root is /var/www/xibo and therefore your CMS library is currently at /var/www/xibo/library/ then the setting in the CMS should be /var/www/xibo/library/
If that won’t fix it, you’d need to enable debugging (on the report fault page) and auditing for your client (on displays page) and see if there is anything else in the logs.