After the upgrade of Remote Application Server, all Gateway agents switched to "Not Verified" status.
Redundancy.log on the Master Publishing Agent server (dir C:\ProgramData\Parallels\RASLogs) shows the following error:
[E 00/00000018/T00000570] Sat Oct 21 21:57:34 2017 - Failed to open Service RAS Publishing Agent (The specified service does not exist as an installed service. [0x00000424])
Also, services.msc applet is not listing RAS Publishing Agent service.
On the Master Publishing Agent go to Control Panel > Programs > Programs and Features > Uninstall or Change the program > highlight Parallels Remote Application Server and click on Repair.
After repairing the issue should be resolved. Please confirm that by checking the services list. RAS Publishing Agent service must persist in this list: