In SharePoint 2013, I ran into an error today where when I clicked Follow, I was redirected to the following error:
Unexpected response from server. The status code of response is ‘500’. The status text of response is ‘System.ServiceModel.ServiceActivationException’.
This is actually not a tough one to solve. There are two things that you need to check. First, look at the memory, since activation exceptions generally mean that a OOM exception was thrown. Importantly, look at the noderunner.exe and ensure that it isn’t tanking the box. Secondly, check the following in the web.config and ensure that it has the following: