I cannot encrypt volumes because 'Encrypt' command in 'Volume'- menu is grayed out.

To get access to all commands, please run BestCrypt Volume Encryption as Administrator.

To do so, right-click on the BestCrypt Volume Encryption shortcut and select 'Run as Administrator' from the pop-up menu.

You will be prompted for confirmation. Click 'Yes'.

Encryption is also not available when connecting through Remote Desktop protocol.

BestCrypt Volume Encryption functionality over the Remote Desktop Connection is limited for security reasons.
Access to your computer locally or use Jetico Central Management to remotely deploy BCVE and encrypt your computers.

More info: https://www.jetico.com/data-encryption/encrypt-hard-drives-bestcrypt-volume-encryption/jetico-central-manager#jcm