NAVMASH disappearing trick?

Hi Guys! My Navmash that’s set up for the AI character that suddenly is not showing anymore. I have tried pressing P then move it, scale it, re position it but still nothing. Also re calculation option is also on. I notice that night before other Navmash was still working and the other two not showing green. Tonight I reload and rebuild the project and now all Navmashes are not showing green. How ever two days ago everything was working just fine. Really strange. If any one can shed some light on these mysterious Navamash disappearing trick Please help the these noob. Thanks…!!!

Also for some strange reason All navmashes at the bottom of the level near origin work OK but at the top of the level non of them show green. Strange for sure.