WhatsApp & Teams & Slack & others read status not syncing iPhone/Mac

Hi,

I've been noticing a read/unread sync issue affecting multiple apps across my Apple devices—specifically WhatsApp and Microsoft Teams, and Slack.

The problem: when I read a message on my Mac, it still shows as unread on my iPhone, and vice versa. The read state simply doesn't sync between devices.

I understand that this kind of sync typically relies on either the app's own cross-device notification system or Apple's infrastructure (e.g., notification dismissal sync). In this case it seems like neither is working properly — the badge count and unread indicators remain stale on whichever device didn't open the message first.

Has anyone else run into this? Is there a known fix, or is this a known limitation with how these apps handle read receipts across platforms?

Device info:

- iPhone 17 (iOS up-to-date)

- Mac m4 pro , m1 mini (macOS up-to-date)

Affected apps: WhatsApp, Microsoft Teams and Slack mostly

Any help appreciated.