Domain checkbox locked

[frongiam]

Hello everybody,
I have problem on a ts-431u.
Warning on winbindd administrator failed access and Domain enable/disable seems to be locked.
I have no possibility to logon or enable/disable the domain and a blue writing says "The default gateway interface has not been set up correctly".

As you can see in the attachment, the checkbox "enable...." is grey as well as Apply and Reset buttons.
What am i doing wrong?

This happened when i updated the new firmware 4.3.5.0722.

Can anybody please help?

Thank you!

UPDATE: We'd like to demote the nas from DC but as you can see we can't 'cause checkbox isn't available. There's a way by command line?