Configuring Anonymous Access for Sync Endpoint

I have attempted to sync with the server (sync endpoint) using None (Anonymous Access) setting in ODK-X Services, but the sync fails with ‘authentication error’. I checked the Users and Roles on my server and ‘anonymous’ is included, as shown below:

I cannot sync nonetheless. (I checked all other settings: server url and non secure authentication being allowed, all settings are correct). Is there any reason why this is happening? How is a server configured for anonymous access?
Thank you!