Last night we installed two updates on a 2016 Data Center edition server, KB4556813 or KB4552926. 2926 specifically dealing with .NET. The server is configured as a web application server which runs APIs configured to use .NET. When going to the API on an individual server, we were receiving a 500 error. Looking at the event logs on the server it was telling us it could not find the .NET Core framework for the application. What we ended up doing is going in the program and features and clicking on the repair option for the framework and running the repair. After that, the API starts to work. Please let me know. Thanks!