Permissions was the first thing I thought of, which is why I checked them all thoroughly and there is nothing to prevent me writing to the backup folder - I have full control and ownership. I created a new file in that folder with no problems. I set the backup folder to a different location where I also checked all the permissions and ownership and checked I could create a file. I could write to that folder directly, but I got the same access is denied error from eM Client. In case it made a difference, the original location is on OneDrive, the new one is just on the boot disk.
I wonder if eM Client creates the backup in a different location, then zips it into the specified directory? That could explain what I am seeing.
Did another check and the way Backup works is by setting up a Task in Windows Task Scheduler. When I looked in Task Scheduler, I found I could not delete the task if I ran it as myself but using UAC to input an Admin password. When I ran it as Administrator, I could delete the task, so I closed down em Client and deleted the task. The I opened eM CLient again and tried to set up Backup. This time, I got the following error:
I’m wondering if anyone is managing to backup successfully, as this seems as if it is in the program itself. As backup is failing silently for me, I would not have known had I not gone into settings to check.
Edited to add I am able to run a Backup manually.