I had the same issue, but found the solution.
Try this URL from the Asus Events site and then scroll down to the bottom and select your region/language:
Here is the URL for the "United States/English" region for the 3-month membership (if your device is eligible):
Here is the URL for the "United States/English" region for the 1-month membership (if your device is eligible):
You can see which of your devices are eligible by going to your My Product page and clicking on a device inside the tabs (e.g. ASUS, ROG, etc.):
You can see which devices are pending/received approval by going to your Application Status page:
If your device is approved, you should see an Adobe redemption link on your Application Status page that starts with the below URL followed by an ID:
If you still see a Server Error somewhere, it either means your device is already pending approval, already received approval, your computer is not connected to internet, or that there is some Asus server issue.
I believe the Adobe Offer expires on August 31st, 2023, so you should hurry. You will need to upload photos of your purchase invoice and your device's Serial Number and possibly also Check Number, which should be on a sticker on the box that the device came in.
@Smokn3D Feel free to mark this reply as the Solution if this helped you out, so that others with this issue can better find the answer.