Thank you Sue for the insight.  I understand that data mods for Reporting Services are not recommended, but we needed to disable users for compliance reasons.  I had created a data mod for the Users table and set the AuthType field = 0 for the expired users. 

There were a few users that had active subscriptions.  I created another data mod to change the OwnerID of the Subscriptions to an active user.  That fixed it!