Are there any other conditions being applied to that field or the tab the field is on? You can not condition a field more than once. If you've it conditioned with conditional self then another field is using conditional others on it then they'll conflict.

Works perfectly fine when editing your self. It doesn't work for other users because you've "Allow Moderators to Edit User Profiles" set to "No" within CB > Configuration > Moderation so CB Moderators can not edit other users profiles (this includes ajax). As explained you need to be able to reach profile edit and edit the field of that user otherwise ajax won't be able to either. The ajax access parameter is in addition to normal edit access permissions as the parameter states; it does not override normal edit access permissions.

You need to ensure moderators can edit other users profiles if you want to edit other users fields with ajax. This is done with the parameter "Allow Moderators to Edit User Profiles" within CB > Configuration > Moderation.