Link local UNIX account with AD account: the require AD logon to host option is grayed out and not available
The AD account UID number was in the range of the host system user setting
From MCU , go to Preferences | System Settings | General | 'Host System Users'
For example if the ratio is set to 0:499. That would mean that all users UID between the range of 0 and 499 are designated as system users. If you set it to 0:100 that should allow any user over 100 to be mapped. You will have to re profile the machine and refresh the local login page.