Find my iphone x

The phone must be turned on and connected to the internet in order to send a signal from its location. Check this link...

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

There a lot of reasons that could be; “turned off” and “dead battery” are the leaders.

Mark as “lost” and add a recovery message.

Be VERY VERY wary of any calls / texts / emails purporting to be from Apple. (It’s a common scam using stolen SIMs)

Sorry for you loosing your phone.

However we’re only fellow users here; not “Apple.”

Only you can find your iPhone using the Apple-provided “FindMy” tools.

There is no other “finding” assistance available either from us or from Apple Support.

Go back and re-review info at the “Lost or Stolen” link; taking additional actions as appropriate for your situation.

Recommend leaving the phone “on” your AppleID - even if you’ve “erased” it with FindMe.

You ARE - after all - STILL the owner; keeping it on your AppleID will prevent to phone from EVER being re-used by anyone else.