Native app sign-up callback `access_denied: Unauthorized` (only in production)

I have a python native backend. I’ve gone through the tutorials and all work fine locally with the localhost callbacks. However in production on a k8s server behind an ingress controller. I get the following error:

[2022-01-10 13:55:06,987] ERROR in app: Exception on /auth-callback-su [GET]
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.9/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/app/web/users/auth0.py", line 31, in callback_sign_up
    auth0.authorize_access_token()
  File "/usr/local/lib/python3.9/site-packages/authlib/integrations/flask_client/remote_app.py", line 76, in authorize_access_token
    token = self.fetch_access_token(**params)
  File "/usr/local/lib/python3.9/site-packages/authlib/integrations/base_client/remote_app.py", line 112, in fetch_access_token
    token = client.fetch_token(token_endpoint, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/authlib/oauth2/client.py", line 203, in fetch_token
    return self._fetch_token(
  File "/usr/local/lib/python3.9/site-packages/authlib/oauth2/client.py", line 226, in _fetch_token
    return self.parse_response_token(resp.json())
  File "/usr/local/lib/python3.9/site-packages/authlib/oauth2/client.py", line 380, in parse_response_token
    self.handle_error(error, description)
  File "/usr/local/lib/python3.9/site-packages/authlib/integrations/requests_client/oauth2_session.py", line 117, in handle_error
    raise OAuthError(error_type, error_description)
authlib.integrations.base_client.errors.OAuthError: access_denied: Unauthorized
Exception on /auth-callback-su [GET]
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.9/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.9/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/app/web/users/auth0.py", line 31, in callback_sign_up
    auth0.authorize_access_token()
  File "/usr/local/lib/python3.9/site-packages/authlib/integrations/flask_client/remote_app.py", line 76, in authorize_access_token
    token = self.fetch_access_token(**params)
  File "/usr/local/lib/python3.9/site-packages/authlib/integrations/base_client/remote_app.py", line 112, in fetch_access_token
    token = client.fetch_token(token_endpoint, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/authlib/oauth2/client.py", line 203, in fetch_token
    return self._fetch_token(
  File "/usr/local/lib/python3.9/site-packages/authlib/oauth2/client.py", line 226, in _fetch_token
    return self.parse_response_token(resp.json())
  File "/usr/local/lib/python3.9/site-packages/authlib/oauth2/client.py", line 380, in parse_response_token
    self.handle_error(error, description)
  File "/usr/local/lib/python3.9/site-packages/authlib/integrations/requests_client/oauth2_session.py", line 117, in handle_error
    raise OAuthError(error_type, error_description)
authlib.integrations.base_client.errors.OAuthError: access_denied: Unauthorized

This is how my callback url looks:

@bp.route(CALLBACK_SING_UP)
def callback_sign_up():
    auth0.authorize_access_token()
    r = auth0.get("userinfo")

    userinfo = r.json()
    email = userinfo["email"]

    return render_template("users/signed_up.html", user=email)

The logs in the management console say this:

{
  "date": "2022-01-10T13:43:16.224Z",
  "type": "feacft",
  "description": "Unauthorized",
  "connection_id": "",
  "client_id": null,
  "client_name": null,
  "ip": "xx.xx.xx.",
  "user_agent": "Other 0.0.0 / Other 0.0.0",
  "details": {
    "code": "******************************************b41"
  },
  "hostname": "dev-1z4b6wsv.eu.auth0.com",
  "user_id": "",
  "user_name": "",
  "log_id": "90020220110134317181942901644625680577123391796617936946",
  "_id": "90020220110134317181942901644625680577123391796617936946",
  "isMobile": false
}

Any ideas?