Scheduled Jobs no longer running
Based on your comments, I was able to use https://www.epochconverter.com/ and see that cron was last run at 5am (GMT) on August 30th.  You submitted that comment around 10:30pm GMT.  That strongly suggests your cron is a) working correctly, but b) isn't running at least hourly.  This causes the "Cron not running" warning.  It's possibly also the cause of the scheduled job not working correctly, though not definitively.

Please update your cron settings to run at least hourly (I recommend every 15 minutes if you use CiviMail).  Once that's done, either a) please let us know if it solved your problem, or b) edit your question to reflect the updated situation.