Getting External Process to work with plink.exe

I have been successful in configuring ipMonitor to use psexec.exe on Windows servers to start a remote program and get the result back to ipMonitor.

In the manual I read the same should be possible on Linux servers using the plink.exe utility. I installed plink on the ipMonitor server and from the commandline on the server it is working fine like this:

plink.exe USER@SERVER -pw PASS -ssh ./test.sh

But when I configure ipMonitor like this:

Monitor Name: External Linux Process
Executable Name: plink.exe
Directory: C:\Windows\System32
Command Line Parameters: USER@SERVER -pw PASS -ssh ./test.sh
Startup Directory: C:\
Credential for Monitoring: Administrator Credential

This does not work, the error is: Last Result:Access rights are insufficient

Any advice, would be welcome,

Thanx,

Martijn