You are using the extension level "/restapi/v1.0/account/~/extension/{extensionId}/", are you sure that you made a call to one of the phone numbers of that extension?

Can you try the account level and run your test?

/restapi/v1.0/account/~/telephony/sessions?direction=Inbound&missedCall=true

The extension ID is correct I assume, since I'm getting all the other extension-specific notifications.

When I subscribe to the account-level notification instead, I do get the notification, but I'm not able to specify which extension to monitor.

So to summarize, this is my experience:

• The extension ID is the correct one (I'm getting all the notifications for that extension when specifying the extension ID)
• The missedCall=true filter works only at the account-level notifications

To add more information, here's the event I received when the subscription was set at the account level:

I then changed the subscription to receive events at the extension level, using the same extension ID as above:

And after that, I stopped receiving the notifications.

I asked you are you sure the incoming call was dialed to a phone number belong to that extension (id: 287893004)?

I tested on my account and I got it works for both account level and extension level. Pls double check the phone number.