[Koha] OPAC Search: No result found!

i am using koha 17.11.02 installed on ubuntu 16.04 and MariaDB 10.0.33. when searching the content of my OPAC it displays "No result found! " . and from the koha about page i noticed this error "zebra server seems not to be available. is it started?" then i entered this command sudo koha-rebuild-zebra -v -f library. it was ok. but after a while same error displayed when searching OPAC. what can i do to correct this permanently? I remain very grateful. Murphy Igbudu Virtual Librarian Benue State University Library and Information Services Benue State University, Makurdi. Nigeria. +234-8038434748 -- Sent from: http://koha.1045719.n5.nabble.com/Koha-general-f3047918.html