Certificate enrollment fails with error: 0x800706ba the RPC server is unavailable

In my situation, this error was caused by insufficient permissions. Basically the “fix” was to make sure that the Authenticated Users and Domain Controllers groups were added to the Builtin/Certificate Service DCOM Access group and that the following groups: INTERACTIVE, Domain Users, and Authenticated Users were all members of the Builtin/Users group. For reference, this was happening on two Windows Server 2012 Domain Controllers — one was the CA and the other (the one that produced the error) was trying to request a new certificate.