How to fix 403 MismatchSenderId when sending web push notifications?

I'm trying to send a push notification to a browser, see script below unfortunately it always fails with: pywebpush.WebPushException: WebPushException: Push failed: 403 MismatchSenderId

Any Idea on how to fix this? It works with the same data when sending using javascript..

import pytest
from pywebpush import webpush


@pytest.fixture()
def subs():
    return {'expirationTime': None,
           'keys': {'p256dh': 'BDz4O5Lb96W133iNj7uEmN0nnZuCDQKg8DTqa4P50stLUJ0vXBhwLker4EyMtf_U2Hr-UFf084QCxwZSR_3F70A',
                    'auth': 'JyE37R0w1dNBzuNYFG7FMA'},
           'endpoint': 'https://fcm.googleapis.com/fcm/send/cvNVGGLtZVo:APA91bFqfRXSHhqdzv6MXFKu7SFUvqyPSRlSNxER2B9cIj5OQZAC1THzACTgtg5Ig6RJiVxhVxL49DrOulNsDv6SkK_DwnnGOs4BVIErOOrNgD9kemuRMaft4n-mwlaptN9ZTNuG6mM2'}


@pytest.fixture()
def vapid_data():
    return {
      "subject": "mailto:tech@rect.ag",
      "publicKey": "BEtyWjkXAXTOTN-5X018konhbR5KpAaQbM4jcWptLDzO2Ia-tm93NCY72TMh5kYAjYDThYY40FGh2BFHJeSX-04",
      "privateKey": "Ew2kli-56Ps6FEspgshs9MnFhhuX2mlMdXqhZqisN5w"
    }


def test_push(subs, vapid_data):
    webpush(subs,
            'Your Push Payload Text',
            vapid_private_key=vapid_data['privateKey'],
            vapid_claims={"sub": "mailto:tech@rect.ag"},
            ttl=2419200,
            )