Firstly, you need to confirm the tracking number is correct. Secondly, you can only get the tracking information when the package has been accepted and scanned by carrier. (PS: Affected by holidays or strike or oversea transportation or high season and so on, carrier sometimes may not accept and scan your package in time.)
If your package already accepted and scanned by carrier, you can visit carrier's official website to contact them by online chat or phone call for learn the detailed situation of delivery.
Go to carrier's official website to get the delivered details for find out where your package was delivered to. (PS: Some carriers will ask to enter the postcode to get the delivered proof.) If you still can't find your package, you can contact the carrier by online chat or phone call to get further help.
You can require for redelivery or collect the package by yourself according to the instruction on the card that courier left at your address. Or visit carrier's official website to get help.
Make sure your delivery address is correct, focus on the update of tracking information, and collect your package in time.
Get the proof of 'package lost' from carrier, and use the proof to talk to sender for resend or refund.