I was trying to delete an entry in my online accounts (since I restored Ubuntu 18.04 files over 17.10), and it wasn’t getting deleted.

The solution is to edit the following file:

~/.config/goa-1.0/accounts.conf

Then simply remove the entry you wish to delete.

Open Online Accounts again, and it’s gone!

Enjoy!

Source:

https://bugs.launchpad.net/ubuntu/+source/gcr/+bug/1044549/comments/14