Open Settings → Notifications in the Artec app and tap Notifications not working? The sheet shows two status rows: iOS permission and Device registered. Both need to be green.
If iOS permission is off: iPhone Settings → Notifications → Artec → Allow Notifications.
Check the per-type toggles below (deals, direct messages, community chats, and so on): the type you're missing may simply be switched off.
For a specific group chat: open the room and check its bell: it may be set to Mentions-only or muted.
In iOS Focus modes (Do Not Disturb, Sleep, Work), Artec needs to be in the allowed apps to break through.
Note that muted conversations still count unread in-app: they just don't push.