Kill inactive user sessions on a Windows Server 2012 R2 Terminal server

A couple of things:

1. Computer Configuration settings apply to computers, not users. That's why you needed to add the Domain Computers group to the GPO security filtering... because Computer Configuration settings apply to computers... so the GPO can only affect Computers that are in the OU where the GPO is linked and are in the security group being used as a security filter. As such, the settings will apply to every user that logs onto a computer in the OU where the GPO is linked... because those are Computer Configuration settings.

2. You can't apply Group Policy directly to a group. Group Policies apply to computers and/or users. You can use a group to filter the GPO so that it is only applied to the members of the security group (users or computers).

3. If you want to apply those settings to only a subset of your users then configure those settings under User Configuration... then link the GPO to the OU where your user accounts are... and use Security Filtering to apply the GPO to the subset of users who are members of the security group.

I used to work in an environment that mandated a one minute disconnected session limit. It drove me crazy. I can't tell you how many times an install or config was killed in the middle when I lost my connection to the server. I did however eventually find a workaround. Change the following registry value as shown:

Key:   HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services
Value: MaxDisconnectionTime
Type:  DWORD
Data:  0

This is the value set by the policy "Set time limit for disconnected sessions". It's stored as a millisecond value. If you set it to zero before connecting to the server, your session will not be disconnected. You'll need to change it back when you are done, though. Also keep in mind that this generally requires you to have local administative rights on the subject server but it sounds like you ARE the admin there.