Sorry that I didn't respond to your post until now. I'm not clear what version of Service Desk you are using as versions before 7.3.2. will be using a different search engine that after. I think it sounds like you are on a version prior to 7.3.2. and so will be using the Verity search engine? If so, and you can't use knowledge base at all at the moment, then in this guide follow Q9 - Starting from scratch:
There was some updates that needed to be run on our dev servers. After performing updates, this cleared up the issue.
Sorry for the delay in updating this.
No problem - glad it's all resolved.