Feature Request Summary: 
After merging brands, tickets from previous brands are not available for end-users.
Description/Use Cases: 
All previous brands belong to the same organization {org-domain}.zendesk.com. So we need all tickets that were previously available within separate brands to be visible in the merged support portal:
Two Help Centers are merged into one:
old-brand1.{org-domain}.com/hc/en-us
old-brand2.{org-domain}.com/hc/en-us
new-brand.{org-domain}.com/hc/en-us
A brand can be changed in not-closed tickets, but the main issue is with closed (there is a feature request on this matter https://support.zendesk.com/hc/en-us/community/posts/4409217551642).

Actual result: 
tickets from old-brand1 and old-brand2 are not available in new Help Center new-brand.{org-domain}.com/hc/en-us.
Expected result: 
tickets from old-brand1 and old-brand2 are not available in new Help Center new-brand.{org-domain}.com/hc/en-us.

Business impact of limitation or missing feature:
After brands merge customers lose access to their tickets from "old" brands.