Proton VPN Kill Switch does not work correctly with multiple users on Win 11

Have you asked proton support about this? If not please do so first. Secondly, I believe proton vpn is installed on system level meaning it might run for all accounts. A computer with multiple users that all login to their own proton account might not be possible; just be a technical limitation because of process sharing. Lastly, if you want a reliable killswitch you should do this on router level.