When the user search for something in the service portal homepage and click on one of the results from the drop down in the search bar, the user will be navigate to the platform home page instead of to the selected catalog item.
Page field is not defined in the search sources of the portal.
1) Search for 'portals' in the side nav bar and open it.
2) Select the portal you are using.
3) Open the 'search sources' at the bottom of the portal page
4) Click on 'Typeahead' tab in the search source page.
5) Add the page value in the 'page' field(Example: form, kb_article).