Welcome to the Apple Support Communities!
I understand you have updated your Mac Pro to macOS High Sierra, but your trackpad isn't responding to your touch.
First, make sure you have updated to the latest version of MacOS High Sierra, which is currently 10.13.1.
Next, reset NVRAM on your Mac and System Management Controller (SMC) on your Mac
Finally, take a look at System Preferences to see if there are adjustments to the trackpad that can be made:
macOS High Sierra - Change settings in System Preferences