yeah if the verify all / restart won’t help then fully qualified path to CMS library could help.
So you can have a look at this topic:
1.7.7 unsolved bug?
tl&dr
You would need to know where exactly is Xibo CMS library located on your web server and enter that full path in CMS settings.
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/