When adding new backup job to Mongo DB MMS, we can have this error
com.xgen.svc.brs.svc.DaemonAssignmentSvc: ERROR Assignment failed: No Daemon found with enough free space

But checking the storage, the usage is just under 20%.

Solution: MMS requires manually configure the backup daemon when you add a new backup job to an existing one. Go to MMS Admin -> Backup -> Jobs -> Set binding, click on it and forces choosing the daemon in select list.