I had the exact same problem Here's something you can try:
1. Launch the Acer Care Center;
2. Go to Service and Support (if not already there);
3. It will ask for your serial number, but also provide an automated way of finding it. Use it, then copy your serial number and paste it into the search box, and click Find;
4. This will take you to a Drivers and Manuals page that will again ask for your serial number (or at least it did me). Just paste it in again. You will be taken to the page for your specific model;
5. Click the Drivers option -- lots of them will appear;
6. Scroll down till you find the touchpad driver. There may be more than one. I chose to install the first one, which is the Synaptics one;
7. As soon as it completed, the touchpad was again functional on my R15.
Good luck!
Bill