I had the same problem with my Asus ROG GL502VT. After looking around everywhere, the best solution I could come up with for the time being was to roll back the OS to before the update.
Click on the start/windows button, then click on the gear icon (settings). Click on "Update and Security", and if you scroll down a little, there's an option to undo the 1803 update. It won't harm your files, but will change programs you installed since the update. Since neither Asus or Microsoft could give me a solution, I did this. But it is, in the end, a temporary solution.
Now, the downside is that rolling back the update will cause bugs that were in the old version to come back. So, after undoing the 1803 update, my problem is that I can't access "Update and Security" under Settings any more. This seemed to be an issue in the old version. Ultimately, it comes down to whether this cost is worth the benefit of getting your touchpad working again. For me, it was worth it, as there are other ways to command your computer to do update-related things without accessing that option from Settings.
Let me know if this works. In the meantime, we need to hound them for a permanent fix.
EDIT:
The following is probably what Asus Support will tell you:
"Please follow the steps below to perform a system restore on your unit:
Step 1: Please press the Windows key and R for the Run utility.
Please type the command rstrui.exe and then press enter to initiate System Restore.
Step 2: The System Restore wizard should appear.
Step 3: Please select next for a list of dates and times to restore the unit to.
If there is an option that allows you to see more restore points, please select this option please.
Step 4: Please select the appropriate date and select Next to start the process.
Step 5: Please select Finish to confirm doing restoring the process to the date selected.
We do value your business, thank you for being a part of the ASUS family.
If you have any further questions, comments, or concerns please do not hesitate to let us know, we will be more than happy to assist you. "
That didn't work for me. Roll back the update like I described above and it should work.