Yes. The app works from your notifications, so it can only check messages that produce one. If you have muted a chat, or you are already reading a conversation when a message arrives, it may not be scanned.

It also cannot catch everything it does see. New scam tactics appear constantly, and the AI will sometimes get it wrong in both directions. Treat an alert as a prompt to slow down, not a guarantee, and treat the absence of an alert the same way. When in doubt, check with someone you trust through another channel (e.g. face to face!), or call the ScamShield Helpline at 1799.