Try to check `sys_transcoder_queue` table for your UNA site:

• if there are all files with `status` = 'pending', then most probably cron isn't working
• if there is file with `status` = 'processing', then some file is processed now and you need to wait while file is completed, then other videos will be processed.
• if there are files with `status` = 'failed', then check `log` field for the file for particular error