Have an active subscription for SMS, but not receiving any webhook events

I use AWS lambda running node JS. In my service, I have established a subscription, but I receive no events whatsoever.

this is the subscription:

{
    "uri": "https://platform.devtest.ringcentral.com/restapi/v1.0/subscription/eb55a123-1f0f-46c4-9c90-cbe8554616c7",
    "id": "eb55a123-1f0f-46c4-9c90-cbe8554616c7",
    "creationTime": "2020-07-08T20:18:12.960Z",
    "status": "Active",
    "eventFilters": [
        "/restapi/v1.0/account/247984004/extension/247984004/message-store/instant?type=SMS"
    ],
    "expirationTime": "2020-07-15T20:18:12.960Z",
    "expiresIn": 538066,
    "deliveryMode": {
        "transportType": "WebHook",
        "encryption": false,
        "address": "https://api.dev.orangetheoryfitness.net/sms/v1/smsreply"
    }
}

Any help appreciated