First, please verify that STAF is not running on the prime client. Sometimes STAF can start in the background so we want to make sure if it is not running.
At the command line, type the command
staf local ping ping
if you see the result
"Error registering with STAF, RC: 21"
please delete the scheduled task that you created for STAF on the prime client, and remake it using the section "Install the General Software > Configure STAF to Start Automatically". Make sure that you select the "When I log on" radio button instead of the "When my computer starts" radio button.
When you log on to the prime client, you should see the STAF window just like on the virtual clients and the command "staf local ping ping" should have the output "PONG".