Using ES256 algorithm

[chrisL255]

The following js code successfully generates a JWT using the algorithm HS512:

var nJwt = require('njwt');
  let signingKey = "secretKey"
  var claims = {
    iss: 'ABCDEFGHIJ',
    iat: Math.floor(Date.now() / 1000),
    exp: Math.floor(Date.now() / 1000) + 120,
    aud: 'https://appleid.apple.com',
    sub: 'uk.co.myco.myApp'
  }
  var jwt = nJwt.create(claims,signingKey,'HS512');
  var token = jwt.compact();
  return token;

> took 215.16461ms
> result: 
"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJpc3MiOiJBQkNERUZHSElKIiwiaWF0IjoxNjg5MzMxMzMxLCJleHAiOjE2ODkzMzQ5MzEsImF1ZCI6Imh0dHBzOi8vYXBwbGVpZC5hcHBsZS5jb20iLCJzdWIiOiJ1ay5jby5teWNvLm15QXBwIiwianRpIjoiNzU3MWI0NDYtMDcwYy00Zjc2LWEyMjMtMzgxNzAyNTc4NDRlIn0.sFq2BRrCzQIJ4gqaypvk36ai2r4JCdyPXq0OxVNw2yOaJ7n1z87PpqjJUJbNkEFi1t-ydqK-mML1CiKlNcbb2g"
> result (JavaScript): 
EJSON.parse('"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJpc3MiOiJBQkNERUZHSElKIiwiaWF0IjoxNjg5MzMxMzMxLCJleHAiOjE2ODkzMzQ5MzEsImF1ZCI6Imh0dHBzOi8vYXBwbGVpZC5hcHBsZS5jb20iLCJzdWIiOiJ1ay5jby5teWNvLm15QXBwIiwianRpIjoiNzU3MWI0NDYtMDcwYy00Zjc2LWEyMjMtMzgxNzAyNTc4NDRlIn0.sFq2BRrCzQIJ4gqaypvk36ai2r4JCdyPXq0OxVNw2yOaJ7n1z87PpqjJUJbNkEFi1t-ydqK-mML1CiKlNcbb2g"')

Unfortunately I need to use the ES256 algorithm. But

var nJwt = require('njwt');
  let signingKey = "secretKey"
  var claims = {
    iss: 'ABCDEFGHIJ',
    iat: Math.floor(Date.now() / 1000),
    exp: Math.floor(Date.now() / 1000) + 120,
    aud: 'https://appleid.apple.com',
    sub: 'uk.co.myco.myApp'
  }
  var jwt = nJwt.create(claims,signingKey,'ES256');
  var token = jwt.compact();
  return token;

Reports an error:

> ran at 1689331442574
> took 
> error: 
'crypto' module: error signing message

I understand from the documentation that nJWT supports ES256. Can anyone advise the additional requirements in changing algorithms from HS512 to ES256 that I have missed?