The CM1312 needs to communicate with the HPToolbox software loaded on a PC.
HP stopped enforcing the installation of the HPToolbox software a while back. It is now an additional installation task that you must re-run the install to find. This is why a simple uninstall and reinstall did not restore the functionality for you.
Re-run the install again and select the addtional features option. Select the HPToolbox and make sure that application is up and running. Once it is you will be able to scan to computer again.