2008 R2 IIS 7.5
Like fyi. After recovering the servers and spending endless hours resolving error 401.3 after changing the AppPool ID for the domain account, we came to the conclusion that the GPO is killing IIS. Make sure that you test the server in the Computer container and that no GPO changes groups with restrictions outside Administrators.
In our case, NT Authority \ Authenticated Users was removed from the local user group, and it shut down IIS.
ItchyTheCat
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