Server 2012- Active Directory Domain Serverices Issue

Hi everyone, I am receiving an error whilst trying to create myself a VPN server on Windows Server 2012 r2. I clicked on the tools menu on the Server Manager window and selected ''Active Directory Users and Computers''. A window opened up however there are supposed to be a list of users in this window but instead an error message pops up saying ''The directory schema is not accessible because: An invalid directory pathname was passed. For this reason, the New menu may be inaccurate, and extension snap-ins may not work properly.''. I clock OK and then another error message pops ip saying ''Data from Active Directory Users and Computers is not availalbe from Domain controller (null) because: Unspecified error. Try again later, or choose another DC by selecting Connect to Domain Controller on the Domain context menu.''

I am at complete loss on how to solve this problem, if someone could help me out, I would really appreciate it. 


Right, I have got it working, I needed to install Ad Domain and create a forest. I set up the VPN connection on the server and the client computer but I cannot connect. I forwarded all the ports on my BT Home Hub 5 router (Which doesn't seem to forward ports even when chosen which ports to forward). I get this error message on the server


These are the ports I forwarded from my router

This isn't something I've had to do recently or on 2012 R2 but this guide might be of help:




That is actually one of the guides I used to set up the VPN, thanks anyway!