Milestone Xprotect Client 2018 R1 and I want to investigate one camera by pressing the independent playback, once I press the Icon all live viewing in my 3disp will be stop the live view in 8secs. what settings I need to adjust?

As this does not pertain to development but to a general situation you will most likely get better help from the partners active in the Support Community - https://supportcommunity.milestonesys.com