can not select recently added user permission

I am new to this userspice, and I use Userspice 4.3 (beta).
I added user permission, let's say 'BOSS'. When I edit my existing user and change it to 'BOSS' user permission, the checkbox is disabled, so I can not select it.
Is it bug? or it supposed to be that way.
How can I set permission to a user if I can not select it?

This is most likely due to the permission restrictions feature we added to 4.3 beta. This is controlled in the settings panel. If the user does not have the permission level, they cannot add or remove it to another user, unless they are within the master account array. You can bypass this by adding users from the permission level page itself.

B.