I’m also having an issue as I’m not able to add the custom claims to the access token. It would be interesting to hear if anyone has a solution to adding rules with custom claims to the /token endpoint with an example. I’m facing the same problem.
Looking around I found one discussion that suggested hooks like this instead for the token/ endpoint:
See: Auth0 Hooks
And: How do I get a rule to run when a client (not user) logs in?
And this discussion may implicitly suggest that indeed, it only works to add custom claims to id tokens with rules:
Can someone clarify if hooks are the solution and why? The explanation would help a lot of us.