We had an issue recently where none of our DA clients would connect.
In the Direct Access log the IPHTTPS adapter was failing with the following error “0x80092013”
From Research this error means that the Certificate revocation List is not available, however this was a third party certificate and when browsing to the CRL specified in our DA certificate we could download the crl file.
I checked the proxy settings on the Users IE setting and via Netsh Winhttp Show Proxy and they were both to set to Direct Access/Blank.
What the issue turned out to be was that the System Account on the machine had it’s proxy set. You can check this via running psexec -s -i "%programfiles%Internet Exploreriexplore.exe" (You need to download from http://technet.microsoft.com/en-gb/sysinternals/bb897553.aspx) . I then checked the proxy settings and it had a proxy configured.
I removed the proxy setting and restarted IPHTTPS service and all worked ok.
The issue was we had a Group Policy changing the system account proxy.