Backup plugin - Cant select any volume

Hello there,
long time OMV user but first time poster

My problem is that I can' select any volume in the Backup plugin.
When I click on the System Backup tab, and then on Volumes, the drop list appears but close immediately.

There is already a ZFS array in use (95% for Plex as a media server), and no problem whatsoever with it.

Is there something special to do or activate before using it ?

OMV version : 2.2.4

Thanks in advance

Oh okay, good to know this is not a problem with my settings !

Thanks for the good work you'll do