We have been instructed by the IT director to created an active directory service account and give it "access to a SQL 2016" database. In our test environment, we have several active directory user accounts that have been granted Sys Admin on our test databases and we can connect fine. Today we created the same kind of AD account and logged into our SQL server and opened Management Studio, from there we tried to connect to our production database with WIndows Authentication and our active directory service account but got the error "18456". We created a local SQL server account with the exact same username and password and are able to connect SQL Server Authentication, however that is not what our director asked for. Does anyone know the error we are getting and what might be different about our production SQL server?