Here's what Apple suggests in this case (you may wish to go to the dpcument and read it there since hwne I copy and paste thigns here the formatting is usually jumbled).
If Find My is offline or not working - Apple Support
I see my device in Find My, but it's offline
Learn why you might see "Offline," "No location available," or "Location Services Off," and what to do.
Why is it offline?
- Your device is powered off or its battery has run out.
- It's not connected to a known Wi-Fi or data network.
- If you turned on Send Last Location, more than 24 hours has passed since it connected to a Wi-Fi or data network.
- You might be in a region where we don't offer this feature due to technical limitations or local law.
What can I do?
You can still play a sound, send a message, issue a
lock request, or start an erase of your iOS device with Find My. Your
device receives the command after you turn on your device and connect to
the Internet.
Learn what to do if your device might be lost or stolen.