Facebook Conversion API: No test events in Events Manager, even though requests graph requests got a 200 response

Question

I'm facing an issue with the Facebook Conversion API, and I'm quite stumped. I'm setting of FBCAPI on an eCommerce store, using Google Tag Manager Server Side, and Facebooks own FBCAPI tag.

All events/requests from the server site returns a 200 response with these parameters:

{"events_received":1,"messages":[],"fbtrace_id":"AQ8y2LHAphY57ukwKMglBR7"}

But in Facebooks Events Manager, the only events that show up are PageView and custom events. No eCommerce event sent by the tag shows up in the test event view, event though it also receives the same 200 response.

I've been playing around with the parameters, but I can't get it to work. Any advice as to why the eCommerce events won't show up in the test event view, and what to do to solve it, would be greatly appreciated.

For reference, the request body on a typical PageView (which does show up in the event manager test view) looks like this:

{
    "data": [
        {
            "event_name": "PageView",
            "event_time": 1662107453,
            "event_source_url": "https://store.dk/shop/vitra-akari-gulvlampe-11696p.html",
            "action_source": "website",
            "user_data": {
                "client_ip_address": "175.158.49.133",
                "client_user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36",
                "em": null,
                "ph": null,
                "fbp": "fb.1.1660481829436.1077185336",
                "fbc": ""
            },
            "custom_data": {
                "contents": null,
                "currency": "DKK"
            }
        }
    ],
    "partner_agent": "gtmss-1.0.0-0.0.5",
    "test_event_code": "TEST52598"
}

The request body on a typical ViewContent (which does not show up in the event manager test view) looks like this:

{
    "data": [
        {
            "event_name": "ViewContent",
            "event_time": 1662107596,
            "event_source_url": "https://store.dk/shop/vitra-akari-gulvlampe-11696p.html",
            "action_source": "website",
            "user_data": {
                "client_ip_address": "175.158.49.133",
                "client_user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36",
                "em": null,
                "ph": null,
                "fbp": "fb.1.1660481829436.1077185336",
                "fbc": ""
            },
            "custom_data": {
                "contents": [
                    {
                        "id": "20164901",
                        "item_price": 5090
                    }
                ],
                "content_type": "product",
                "currency": "DKK"
            }
        }
    ],
    "partner_agent": "gtmss-1.0.0-0.0.5",
    "test_event_code": "TEST52598"
}

I can't see that any of these parameters are incorrect, nor that any are missing (parameter reference)

UPDATE: This issue seems to have resolved itself over the weekend. I have made no changes, but today (Monday) all test events show up in the test view.