This is a very rare case of Board Engine crashing due to faulty .NET 4 updates.
Symptoms: BoardEngine crashes, Board Engine can not be started, IIS Service is not available
In the event viewer you find entries like this:
Description: Cannot start Board 10 Server. Original cause: Only one usage of each socket address (protocol/network address/port) is normally permitted.
The issue is caused by a problem in recent .NET 4 updates, Microsoft explain the issue in this article: https://support.microsoft.com/en-us/help/4345913/access-denied-errors-after-installing-july-2018-security-rollup-update
Follow the instructions described in the article and install the correct patch according to your operating system.