Unable to delete webhook subscription

I have a functioning webhook but need to update the callback URL as this will be changing. First I tried simply creating a new subscription but found I couldn’t since you can’t have more than 1 active at a time. So then I tried to delete the existing subscription to recreate it - but running into the following error:

{
    "message": "Resource Not Found",
    "errors": [
        {
            "resource": "PushSubscription",
            "field": "",
            "code": "not found"
        }
    ]
}

I have double checked that it’s the right sub id using the GET request to https://www.strava.com/api/v3/push_subscriptions.
This query is successful which also rules out an issue with my client_id and client_secret (I am using postman and leveraging variables so know they are the same).
Body is set to None. Here is the query: https://www.strava.com/api/v3/push_subscriptions/[my_id]?client_id={{client_id}}&client_secret={{client_secret}}