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