Script work in terminal but fails when pushed from policy

Scripts pushed via policy run as root. So root would need to be logged in for the finder to display that dialog.

You probably want to alter the script so you are either directly instructing the SystemUIServer to display the dialog (that way it will pop up for any open UI instance) or have it run as the current logged in user.

This might work, a few issues with your script but I think I might have fixed them.

#!/bin/bash

messageToDisplay="$4"
policyToExecute="$5"
policyAction="$6"

buttonClicked=$(/usr/bin/osascript -e "button returned of (display dialog "$messageToDisplay" buttons {"Cancel", "OK"} default button 2)")

if [[ "$buttonClicked" == "OK" ]]; then
    open "jamfselfservice://content?entity=policy&id=$policyToExecute&action=$policyAction"
fi

exit 0

Firstly test your script with sudo to see if it works as root. If you find it doesn't, then you can add

thisUser=$(stat -f%Su /dev/console)
su - "$thisUser" -c '

Your script

'

to run it as the logged in user - which when dealing with UI stuff and AppleScript is usually quite a good idea anyway!

Otherwise, have a look in System Preferences > Security & Privacy > Privacy
See if there's something that Terminal's able to access for your machine that's not enabled on the test machine.

Hopefully this might be useful

I realize you already found a solution, which is great! But I wanted to mention that you shouldn't need to use Applescript for this. There's nothing in this that requires it to be applescript, such as choose from list or something. It's just a simple dialog with buttons. If you switch it to jamfHelper, you should have an easier time with it. Example:

#!/bin/bash

messageToDisplay="$4"
policyToExecute="$5"
policyAction="$6"

buttonClicked=$("/Library/Application Support/JAMF/bin/jamfHelper.app/Contents/MacOS/jamfHelper" -windowType utility -description "$messageToDisplay" -button1 OK -button2 Cancel -defaultButton 1)

if [[ "$buttonClicked" == "0" ]]; then
    open "jamfselfservice://content?entity=policy&id=$policyToExecute&action=$policyAction"
fi

exit 0

That said, you might still need to add that sudo -iu $loggedInUser in front of the open command or it may not work due to the policy being run as root and all.