After migration you MUST update WhatsApp to latest version from Google Play Store. If the updated version does not retain imported messages, kindly check the following:

  1. double-check you disabled WhatsApp Google Drive backups - this could interfere with restore from LOCAL backup 
  2. double-check a LOCAL WhatsApp backup was performed before uninstalling older version

Please note: latest WhatsApp will prompt a misleading Google Drive screen like this, but it will ask you for local restore immediately after: