This issue could be due to various reasons such as poor internet connection, outdated app, or blocked contacts. Here are some steps to troubleshoot:
1. Check Your Internet Connection: Make sure you have a stable internet connection. You can try to disconnect and reconnect to your Wi-Fi or mobile data.
2. Update וואצאפ: Ensure that you are using the latest version of וואצאפ. Go to your device's app store, search for וואצאפ, and update if available.
3. Check Contact Block Status: Make sure that the contact you're trying to receive messages from is not blocked. Go to וואצאפ > Settings > Account > Privacy > Blocked contacts and check.
4. Check וואצאפ Server Status: Sometimes, וואצאפ servers may be down. Check on 'Downdetector' or similar sites for any reported outages.
5. Reinstall וואצאפ: If all else fails, backup your chats and reinstall וואצאפ. Go to Settings > Chats > Chat Backup to backup, then uninstall and reinstall the app from your device's app store.