My regular backups suddenly stopped

Hi friends,
I setup regular backup of Dropbox folder on my workstation and everything worked fine. However suddenly backups stopped month ago.

I can see last error log info:

06/19/24 17:30 INFO Writing new file list…
06/19/24 17:30 ERROR Error creating client file list for client Z230 at /var/urbackup/clientlist_b_516.ub. No space left on device (code: 28)
06/19/24 17:30 ERROR Fatal error during backup. Backup not completed
06/19/24 17:30 INFO Transferred 291.347 MB - Average speed: 33.6166 MBit/s
06/19/24 17:30 DEBUG Script does not exist urbackup/post_incr_filebackup
06/19/24 17:30 ERROR FATAL: Backup failed because of disk problems (see previous messages)
06/19/24 17:30 INFO Time taken for backing up client Z230: 3m
06/19/24 17:30 ERROR Backup failed
06/19/24 17:30 WARNING Exponential backoff: Waiting at least 5h 20m before next file backup

I have no option on client to start backup (which was there originally). Client is last version for windows 2.5.25

When I open web interface of server and click Start incremental backup - I get immediately message “Starting backup failed”

Can you please guide me to find what is wrong?

Many thanks

Vladimir