Workflows emailing everyone except certain users

I have an issue where our workflows will email to me and the person developing the workflows, but it will not send to someone in our legal department. Where would I start looking for logs on the server? The only step I have taken was removing that users profile and re-adding it (it showed up weird before). This is on on-premise install of SharePoint 2013.

The error was

RequestorId: 1ad10e9e-cb45-c76a-9ebc-ecd99b4b3ff2. 
Details: System.ArgumentNullException: Value cannot be null.
Parameter name: Input
at Microsoft.Activities.Hosting.Runtime.Subroutine.SubroutineChild.Execute(CodeActivityContext context)
at System.Activities.CodeActivity.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager)
at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)