traderjohnroberts

Thanks, that solution worked. I wanted to backup before updating WordPress in case the upgrade broke something on the site.

For the benefit of anyone with the same problem; I commented out the line calling get_main_site_id() in plugins/updraftplus/backup.php, and sure enough, was able to run a complete backup.

Then updated WordPress (and everything was okay), uncommented the line, and tested backup again, and it’s fine.

So, my issue is now resolved. 🙂

Okay, I didn’t think of that because UpdraftPlus (old version) was working on my multisite up until March ’23. I just recently noticed my weekly automatic backups had stopped 10 months ago!

But thanks for the solution, cheers.