Changing username in Joomla brings up error

When we try to change an account's username in the Joomla backend (via Community Builder) it gives this error:

XML-RPC Error (23000021): Access control exception | DEBUG INFO: Access to the function joomdle_change_username() is not allowed. There could be multiple reasons for this: 1. The service linked to the user token does not contain the function. 2. The service is user-restricted and the user is not listed. 3. The service is IP-restricted and the user IP is not listed. 4. The service is time-restricted and the time has expired. 5. The token is time-restricted and the time has expired. 6. The service requires a specific capability which the user does not have. 7. The function is called with username/password (no user token is sent) and none of the services has the function to allow the user. These settings can be found in Administration > Site administration > Plugins > Web services > External services and Manage tokens. | ERRORCODE: accessexception

Is it something we have not set up?

Hi. Is your system check all green?

It seems like the function has not been added to the service.

System check is showing all green. All Joomdle plugins are enabled as well.

Go to Moodle->Site admin->Plugins->Web services->External services
Click Functions for Joomdle service.
At the botton, click "Add functions"
Search for joomdle: some functions should appear, as it seems they have not been added automatically. One should be joomdle_change_username.
After adding it, process should work.

Yes, that fixes it! Many thanks!