I have installed a program that utilizes SQL Server 2012 on five computers. The computers are in a domain, each user has a unique id. I did not write the program, I am only configuring it. The publisher does not support this setup but has stated others have done it successfully. I do not know who they are so I cannot reach out to them. The server is on one of the computers and not the domain controller. The program has a database connection string editor where the location and user information is stored. I set the permissions for the directory where the mdf files are stored to allow the users access, and mapped drives to each computer.
Everyone connects fine. Except when someone else is already connected. On occasion I've had multiple connections but it seems random. Usually I receive an error stating permission is denied for the user to the main database. Multi access is enabled on the database. Do I need to do something with users or roles in the server management tool? The server was installed as Microsoft Integration only. I've also tried to make changes using the management tool only to be denied due to lack of permissions. I've googled my way through some of this but I am not finding much that just spells it all out.
Thank you for any help you can provide.