Cloudberry Backup Has Completed With Errors

For the past week or so I have been receiving the message, Cloudberry Backup Has Completed with Errors.

When I look at the backup history, it shows that 0 files have uploaded and the last result is:

Insertion failed because the database is full....

The last thing I did before this problem started, is run the 'Shrink Database' option, which shrunk the database from 2.8Gb to 800Mb.  Since then I haven't had a successful backup, and I now notice the database is being reported as 9.03Gb, but running the Shrink Database task does not reduce that.

Can anyone advise what's going on and how to fix it?

Thanks