I just had an issue with service security. Different BO but same behavior. Check to make sure the “allow all” checkbox didn’t get unchecked accidentally.
And looking at your error, I wonder if the specific method was added as security. My error only showed BO.Sales. Not the second part that you have listed.
I would look in process security maintenance for that BO and Method. Security is set on that BO and Method somewhere preventing access. For the method I would check the status of the ‘security manager access only’ checkbox, I would also look at the status of the ‘Allow Access’ tab but I would really look at the ‘Disallow Access’ tab to ensure users or security groups aren’t listed in it. I’ve seen the ‘allow access to all’ be checked for the ‘Allow Access’ tab but then looking at the ‘Disallow Access’ tab it had users and groups in it which overrides the ‘Allow Access’ settings.