Microsoft 2012 R2 Server configured as PPTP Server.
Mikrotik Routerboard (any one) configured as PPTP Client

Mikrotik PPTP Client connects, but fails to obtain IP address.

This happens whether the Mikrotik is behind a firewall or not.

Windows PC's can connect fine, so I'm guessing the PPTP server is somehow blocking non-microsoft clients - if this is possible.

I can't do anything about the server side, it is managed by a third party, just curious if anyone has experienced similar behaviour?

Further to this, when attempting to connect to the MS PPTP server, the log indicates authentication is successful, but terminates stating Encryption got out of sync.

If I continuously ping a device over the vpn, it will eventually work.

What you see on Windows Server RRAS log? I think you use RRAS?