Automated backup fails and no link to show why

Hi, 

I have migrated from 1.9.15 through all the others to now be on 2.3.1

I've set automatic backup to on using the settings as shown below.

But I then went and had a look at the backup report and everyone of them is Error, except the ones which are past the 30 day theshold for not backup in.  Also the name of the course doesn't have the link to view the report to see why it has failed.

can anyone shed any light on why this is erroring?

Thanks

Kieran