Proton Customer Service
I appreciate the help received from Sonny, Kosta, Anton, and others in attempting to resolve my problem with ProtonVPN to reconnect after reboot/shutdown of iMac (OS). It appears that I'll have to manually reconnect to iMac, until Proton issues a update to fix the problem.

Proton Enhancements for iMac (OS):
ProtonMail: sound alert for incoming mail.
ProtonVPN: auto-connect, ProtonVPN icon/checkmark in menu bar should change to a different color indicating connection, need a Permanent/Advanced Kill switch in addition to Regular Kill Switch.
ProtonPass: the ability to use Passwords that auto-fills to connect logons automatically.
ProtonDrive, ProtonCallendar, ProtonAuthenticator do not appear to have issues on iMac (OS). Proton Apps on iPhone (IOS) do not appear to have issues.

It appears that Proton enhancements for iMac (OS) aren't in the forefront for Updates to correct issues.

Thanks,

Frank