Like some web-based games, GeForce NOW uses mouse lock and Chrome doesn't appear to support tapping the touchpad with that mode. You have the option of pressing harder to click the touchpad or using a USB mouse (recommended).
I'm on a Chromebook and tapping my touchpad doesn't register a click in GeForce NOW
Updated:
I'm on a Chromebook and tapping my touchpad doesn't register a click in GeForce NOW