Why can't I set a contact at the Add Samples window?

When I click in Contact* (Select the primary contact for this sample), there is no person list here, even typing into text box, after press enter, it still empty.
The users and Lab Contacts are alreay have members.

it need to add person in “Contacts” of specific Client page first.
not in “Setup” - > " Lab Contacts"

Thanks a lot! It is solved my problem.