some has turned find my off

Find My can only be turned off on the device when someone knows your Passcode to login and also your Apple ID Password to turn it off. That is not likely unless you knew the person that stole it and they had that information.

There is no way to remotely turn Find My on. It must be on before you lost your phone.

If you had Find My turned on when you lost your phone, what makes you think someone turned it off?

No one turned Find My off on your phone unless they knew the passcode, Apple ID and Apple ID Password for your phone.

Maybe you are really saying that you see that the phone is "Offline" when you are using Find My to try to locate the phone?

There is no way to turn it back on if you are not in possession of the phone. For security reasons, you should remove it from your trusted devices. See the "If your iPhone or iPad is lost permanently" section of Find your lost iPhone or iPad - Apple Support

and note in particular the "Update your account information" section.