Error details are not currently logged anywhere; this will be changed in a future version of MDT.
Test the setup by opening Internet Explorer on a machine other than the site server, pointing to "http://servername/MicrosoftDeployment/UnknownComputer.asmx". Substitute your server name and the name of the virtual directory you created in IIS.
If that page fails to open, check:
- .Net Framework 2.0 was not installed, or you need to run aspnet_regiis and restart IIS
- The site server must be properly configured as a Server Locator Point (SLP)
- Does web.config specify the proper SLP server and network access account?
- See Michael Niehaus' blog on this subject
If you get an error page saying "Unable to determine the ConfigMgr site for this client":
- Does web.config specify the proper SLP server and network access account?
- Did you remove the commenting brackets before and after the line with the access account?
If the UnknownComputer.asmx page opens, test each of the functions
- GetADSite requires the IP address and the SMS network address, not the subnet mask, to be tested
- Errors commonly point to problems with the site boundaries, data published to AD, or the SLP
If the UnknownComputer.asmx web page functions properly, but the target computer does not boot into the Unknown Computer process:
- Make sure the task sequence selected creating a boot file, selected to include the unknown computer hooks and specified the correct web service site (the same UnknownComputer URL tested above)