Microsoft XP SP2 VPN Client troubles

Well, first off...nice to be here?! I normally would like to start off by
helping but I've gotten stuck on a problem and need some assistance.

My test systems, for this problem, are both Windows XP SP2, fully patched.

I'm currently putting a VPN in place, the hardware is a Nokia 5i. I have a
CA created, the AD controller, and can request and install certificates
without issue.

On the client I can verify through the MMC and/or by going to
IE/Tools/Internet Options that the certificates are installed. Additionally,
the Root Certificate of my CA has been added to the machine and is listed in
under the "Trusted Root Certificate Authorities".

However, whenever I attempt to connect via the MS VPN client I receive the
error 781 "No certificate found". After several Google searches...I've come
up empty. Each solution I've found merely explains how to install the
certificate.

Additionally, I've verified that the two services Routing and Remote Access
and IPSEC Services are running on both machines.

Any thoughts on what step I'm missing?