Unified Remote Access is a complex technology that relies on many moving parts to work correctly. As such, there are plenty of things that can go wrong. As problems go, things are usually divided into server-side problems stemming from a misconfiguration, and client-side problems, which often happen because something went suddenly wrong (you know...those mysterious malfunctions the user reports started right after he/she browsed to www.doesn'tmatter.com).
The more complex your configuration is, the more things you have that can possibly go wrong, thus increasing the scope and complexity of troubleshooting, so as a general approach, we suggest the following practices:
Make sure your server has not been configured with software that could affect this technology. Security software such as antivirus and Firewall software often takes over some aspects of the networking components, and that could cause problems.
Make sure your server has not been hardened another way, such as...