What's interesting is that in your message you used {instagram account-id} to replace a numeric value that you saw in Facebook response. This number IS NOT your Instagram ID (as in your ID on Instagram). This number is Facebook's Instagram Business ID. It goes like this:
Facebook page (facebook page id) is associated with an Instagram Profile (instagram id) via Instagram Business Account (instagram business id).
In your above message, that ID is "instagram business id".
Why would it be missing? It is important how it was created: Instagram user, on their device, converted their Instagram account to Instagram Business account. When they did the selected a facebook page. This created "instagram business id".
If this user ever loses admin access to the Facebook page (or becomes anything other then admin) - "instagram business id" will become invalid.
How to fix? Simple, go to your device, convert your instagram profile to personal and then convert it back to business. You will get a new "instagram business id" so you will need to query that on your page.