NullInjectorError: No provider for JwtHelperService

A little late to the party, but I ran into the same issue trying to follow the standalone docs and what it doesn’t cover is the need to import the options InjectionToken which is referenced in the constructor of the service:

import { JwtHelperService, JWT_OPTIONS  } from '@auth0/angular-jwt';

...

providers: [
        { provide: JWT_OPTIONS, useValue: JWT_OPTIONS },
        JwtHelperService
    ]