Running this command via Terminal should help:

sudo chown root:root /opt/local/CloudBerry\ Backup/etc/plans/*

It changes the permissions for the plans to root and that usually helps with most of the permission problems.

This is a slightly aging post, but I just wanted to add a note - this did help quite a bit, but I'm still getting more issues than I like. More research to come. My system runs Mint 19.3 (Ubuntu under the hood).

Here's the link to the mac/linux knowledge base with similar advice: link, but Matt's suggestion to specify root is not present in the KB.

Thanks, @Matt for the tip!

final update - this fix offered by @Matt worked perfectly for me. You might also need to restart the cloudberry-backup service

Just working through similar issues, but I'm finding I have no directory:
/opt/local/CloudBerry\ Backup/etc/plans/

My install is in: /opt/local/CloudBerry Backup
And I have no etc/plans sub folders and no *.cbb files anywhere to be found.
My backup was configured to save plan config on the external storage (BackBlaze B2). So, I presume that's the only location of my .cbb files? In which case, how does one manage their permissions?

Further to this, is there a recommended approach to backing up multiple user home directories? Each user setup their own backup plan with their own permissions? Create a backup plan as root which has permission to read all user folders? Or add an admin-backup user to all user groups, and create plans under that user (assuming all user files are readable as their group)?

If you're unsure of the logs location it's better to contact support, the configuration files are always saved locally.

As for the multi-user setup, the most secure option is to change permissions for each plan individually.
Setting root permissions is just the easiest option and suits most of our clients.

I found that the CloudBerry Backup plans directory for my install of Ubuntu 18.04 is in:

Thank you so much!! This worked for me. These are the steps I used (although my chmod 666 is overkill. I need to experiment with that one)

sudo chown root: root /opt/local/Online Backup/00000000-0000-0000-0000-000000000000/plans/{a2483730-77c8-451b-aff6-a87bcfb95b0f}.cbb

sudo chmod 666 /opt/local/Online Backup/{a2483730-77c8-451b-aff6-a87bcfb95b0f\}.cbb

sudo systemctl status cloudberry-backup