New folders on the source system do not appear on the target system after data re-migration

Problem or error: After re-migrating items such as campaigns, sessions, or offers in newly created folders on the source system, the new folders do not appear on the target system.

Solution: To work around this issue, re-start the target server to flush the cache, or wait until the target server updates its cache. Any new folders and their contents will then appear on the target server.