I have a subscription set up for a webhook to call a url on the Instant Message event (/restapi/v1.0/account/~/extension/~/message-store/instant?type=SMS).
When I first create the subscription, the webhook URL is called, and I can confirm at this time that a Validation Token is present, and I am able to establish the subscription.
If I check the Subscription list at this point, I see that my subscription/webhook is active.
When I send a text message to my number, the url is being called by the webhook (as expected), but there is no Validation Token present, so obviously I can't validate to continue the process and receive the POST data.
I have had a subscription / webhook active for this event for the last 1.5 years and it has worked without issue, until 7 days ago when it just stopped working. After investigating I was able to figure out the above (no Validation Token is present anymore).
I've tried removing and creating a new subscription, confirmed the permissions in the app in the developer portal, and I've also tried creating a new app in the developer portal.
If anyone might be able to shed some light on this issue that would be very appreciated. I've contacted Ring Central support, but haven't received any response.