Hi, I am Dave, I will help you with this.
1
Look at the function keys (F1 - F12) on your keyboard, does one of them have a touchpad icon?
If one does, try pressing that key or Fn + that key to see if that enables the touchpad.
2
If that was not the problem, go to the support page for your laptop on the Acer website, then from there, download and manually re-install the version of touchpad drivers they provide.