Symptoms

After renaming an activity and its associated client event the workflow would no longer send task notifications even though it would assign the task.
 

Diagnoses

After checking the EventBus.ClientRecorderError table in SQL we found an error that we were able to tie back in to the problem workflow/client event by starting the workflow and creating an identical error

The error indicated that there was an issue with the FromAddress item reference which was not to be found in the MS Build file.
 

Resolution

By adding the FromAddress to the MSBuild file that was being used, task notifications resumed as normal.