Are your users logging into that machine - or are they logging into their own machines and trying to connect? If they are logging into their own machines, are they authenticating using a domain account or local account?
For this to work, they would need to login to their machines with a domain account - and you would have to add their domain logins to the local group on that machine.
Jeffrey Williams
“We are all faced with a series of great opportunities brilliantly disguised as impossible situations.”
― Charles R. Swindoll
How to post questions to get better answers faster
Managing Transaction Logs