The add-in can fail to load if you do not allow it past your firewall. These are the exceptions you need to make:
https://precedent.authordocs.app
https://author.app/
https://authordocs.mccarthyfinch.com/
https://api.author.app/
https://api-review.eu-author.mccarthyfinch.com
https://author.app/
https://authordocs.mccarthyfinch.com/
https://api.author.app/
https://api-review.eu-author.mccarthyfinch.com