Currently some Proton apps are unusable on a Mac with multiple local users. For instance if you have Mac User A and Mac User B both with Proton accounts (PA and PB)

Mac User A installs Proton VPN and Proton Drive and logs into each with PA

Mac User B uses "Switch Users" to log into their local Mac account and tries to use Proton Apps

*Proton VPN: The app will open and Mac User B logs in with their Proton B account but the VPN will never establish a connection. It will say "connecting" but eventually time out with no error. The user is not protected by the VPN and their public IP is exposed. The only way to fix this is to use Activity Monitor and Force Close Proton VPN on Mac User A's process list, but this requires Admin access and is not always possible. 

*Proton Drive: Mac User B is not able to open the Proton Drive app at all. There is no error message it just does not open.