Can you install the free plugin WPCrontrol and take a screenshot of your cron events?
What are your visitor numbers like at the time of the backup?
Traffic will be minimal – it backups in the middle of the night
https://www.guerilla.co.za/stuff/screenshot3.jpg
Apologies, I need a screenshot of your Cron events to see if any are overdue, like this: https://snipboard.io/QR6Nd4.jpg
It sounds like low visitor number might be the issue.
UpdraftPlus can only make a backup when WordPress is loaded into Memory. This normally happens when someone visits the site.
I would recommend setting up a number of dummy visits to the site via an external cronjob.
These are automated tasks performed by the server.
You will need to set up an automated task to visit your site (please set the cron job to visit: http://yourdomain.com/wp-cron.php?doing_wp_cron )every 5 – 10 minutes (This will also keep the rest of your WordPress scheduler running):
Your hosts may have a tool to set up a cronjob, or you can use an online tool such as EasyCron
