Service Portal Search results not showing up articles of a particular Knowledge Base

[Community Alums]

An article published in a knowledge base does not appear in the search results when searched from service portal's search bar , while the same article when published in another Knowledge base appears in the search results when searched for. 
I have checked OOTB "Facet generation script" it looks fine .

[Dominik Simunek]

Which service portal do you talk about? /sp portal? Please check and confirm that the KB is linked to the Service Portal (in the form of the service portal record, scroll down to the related list). 

The issue might be there, that KB is not linked to the portal (unless you talk about Knowledge Portal /kb).

Another issue might be setup of Can Read of the impacted KB. Ensure that user has read access to the KB and meets Can Read user criteria of the KB.

Share screenshots or more details if above hints do not solve it.

[Community Alums]

Thank you for response, above solution did not work, When i am searching an article linked to a custom KB it does not appear in the search results of the portal search, unlike other articles appear in search results which are linked to OOTB KBs . 
I have attached screenshot for your reference .

[Community Alums]

I tried above solution it didn't work. When i am searching for the article which is linked to a custom knowledge base on service portal, it does not appear in the search results,  but articles which are linked to OOTB knowledge bases appear upon searching.
I have attached screenshots for your reference .

[Community Alums]

Thank you for response, above solution did not work, When i am searching an article linked to a custom KB it does not appear in the search results of the portal search, unlike other articles appear in search results which are linked to OOTB KBs . 
I have attached screenshot for your reference .