Firebase Messaging statistics always shows "0"

**Describe the bug**
I'm using this plugin to receive push notification inside a iOS and Android mobile app. It's working ok except for one thing: when I look a the firebase messaging stats, "received", "impressions" and "open count" are always at 0 even if the notifications are received and viewed on devices. Only the "sends" stats in updated.

Should this be working? Am I missing something to make this work? I can't find anything in the doc.

**To Reproduce**
Steps to reproduce the behavior:
1. Send notification to device through FCM.
2. Receive and click on notification on device.

**Expected behavior**
"Received", "Impressions" and "Open count" should be updated.

**Smartphone (please complete the following information):**
- Any devices with Capacitor 5.
e problem here.

Start by reproducing the issue with an FCM notification on both iOS and Android using Capacitor 5, then review the plugin's Firebase Messaging integration and its documentation for configuration requirements. Compare device delivery and interaction results with Firebase statistics; the work is done when the cause is identified and the received, impressions, and open counts update or the limitation is documented.

Written by the indexing model from the issue text.