Reason: Knowledgebase search does not give relevant articles
Solution: Knowledgebase search is used by clients to search and find their own answers to simple queries. Please perform the following steps :
1) Re-index the Knowledgebase articles from Admin CP > Knowledgebase > Maintenance.
2) Rebuild help desk cache from Admin CP > Diagnostics > Rebuild Cache
Also, make sure that words used for search are not "stop words", specified in MySQL. The list of the words can be found at: