Workfront Bulk Assignments in Workload Balancer ceased working

The Bulk Assignments function in Workload Balancer ceased working for two users (one is a System Admin and the other a Group Admin). The functionality remains in tact for the other two System Admins and Group Admin who use it. 

Key info to note:

• Nothing was modified in the system setup or configuration
• The System Admin (myself) who has lost the functionality can’t assign any role in any project.
• The Group Admin who lost functionality only experiences with specific job roles. 
• All of the System Admins and Group Admins use company provided Mac computers and everyone has installed the most recent Mac system update. (I hoped that may have been the differentiating factor, but no.)

Anyone experienced this before? Any advice on solving or troubleshooting the problem?