Issue Sometimes on importing a solution in CRM v8.x, it might fail with the error: ‘Workflow contains an invalid custom activity’. In an effort to try to conquer the ambiguity, I tried to create said Workflow manually on the target environment. Adding each step went well until I noticed that one of those steps, namely a certain Custom Step, caused the error: ‘InvalidCastException’. The error might look something like this: Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft... Read the full text.