I have examined the protection group settings and do not find an expected setting to "Enable agent admin UI" (like I have with our VAC for Service Providers). I have also examined the job settings. I have also examined the PowerShell cmdlet reference guide. And I have attempted to manually run the backup using the Veeam Agent's CLI. At this point, I can only conclude that Veeam has (unintentionally, I hope) removed the granular control I previously relied on for running a test backup of a specific agent post troubleshooting an issue.
I would love to be told that I am overlooking a feature or button or setting somewhere...
Also, it would appear the Veeam Agent tray icon cannot even load. This is the message I get when I actually logon to the OS profile and apparently the tray icon attempts to auto load. It also shows when I attempt to open Veeam Agent through the Start Menu.

FYI... my open case is 04145841