Can't ping Mac from PC
I had similar problems, tried lots of things and finally tried not only to shutdonw my checkpoint VPN client but also delete all profiles and one would'nt delete as it had some firewall settings enforced...sounded scary so I removed checkpoint completely and viola ping works :)    https://community.checkpoint.com/thread/6627-i-have-endpoint-installed-on-my-system-and-want-to-uninstall-it-because-a-virus-has-masked-it-from-view-i-cant-find-it-on-the-launch-pad-or-in-the-applications-library-how-can-i-locate-it-to-uninstall-on-my-mac