Problem in enabling Shell access to users?

[networkexpert]

Dear Sirs

I've started evaluating the VShell software on my server, but the users I've made in the database of the users, i cannot enable shell access for them the option is grayed out, but i can do it with the users I've added from windows users directory, the only options i can allow or deny to the users I've made in software are logon, scp and sftp, can you please help me regarding this problem?

Your help will be really appreciable.

Best Regards
Usman