We recently released the DirectAccess Step by Step Guide and many customers are using it to start understanding and testing DirectAccess in their labs, which is great. However, if you're planning to virtualize your lab environment on Hyper-V, you should ensure you're using Legacy Network Adapters for the child partition where you're running the DAS. Using the default synthetic NICs is OK for all the other resources in the test lab, but for the DAS itself, it's important to have both the Internet and Corpnet NICs as legacy ones, to ensure proper passing of traffic between both sides of the DAS. If you use the default synthetic adapters, you may end up in a situation where traffic doesn't properly flow from the outside to the inside, even though all your IPsec, 6to4, Teredo, and IP-HTTPS settings are correct. Basically, you'll be in a situation where connectivity will fail at a basic level, with you not even being to successfully ping the internal DNS server using its ISATAP address.
If you've already built your lab on Hyper-V using the synthetic adapters, the fix is pretty simple. Just replace them with legacy ones, reconfigure the IP addressing as specified in the guide and rerun the DirectAccess wizard, again supplying all the information specified in the guide. After doing so, all your traffic should flow properly.