To add to @trumpy81’s comments…
Plex Media Server v1.42.1.10060 is now available. It fixes the “problem with a core component” bug. You should use it instead of 1.42.1.10054
Installation with a Plex Claim Token, including screenshots, is covered in FAQ 31: Reset / Reclaim PMS on DSM 7 (Not Authorized - Locked Out).
