First, if you are running Jenkins on the test system, you should not need to use PSEXEC. You can run your tests directly from the Jenkins job, assuming the Jenkins slave is not running as a service. If it is a service, it must be set to have access to the desktop in the Windows Services MMC plugin.
Second, and probably most important, the system you are running the tests on MUST be logged in AND MUST have a visible desktop. It cannot be locked and it cannot be a Remote Session that is disconnected. It MUST be logged in and the desktop MUST be visible or Ranorex will not be able to find objects. This is a function of the Windows security model and there is nothing that Ranorex can do about it.
My recommendation is to log into a third system and use that third system to remote-desktop into the test system, leaving the test system's RDP session open on the third system at all times. You will need to turn off the screen saver and the lock screen on the test system so that the test system is always available to run tests.
Experiences, small talk, and other automation gossip.