Google says No active devices in Find My Device

I have lost my phone this morning. At that time when I go to find my devices there were two mobile phones listed in find my devices including the lost one (and my previous mobile phone). The person who took it switched off it and due to that, in find my devices, it shows the last location as my home. But in the evening when I check my activities on google, it said I have connect to google by my mobile few hours back. So I thought that thief turned on my device. And I checked find my devices and it says No active devices What are the possibilities which can be happen. In my phone I have setup every settings to turn on find my device. Even location and mobile data. And in the morning also the device listed in the find my device console. I thought that missing devices won't disappear for 6 months in any case. The other thing is both of my mobile devices are listed in some another find my phone menu. In the morning, using find my device option in web, I have locked and set a message for my phone. But I did not erase the data. (because it said erase after erasing I will not longer able to locate it). Also I have used my fingerprint to lock the device and there was pin locked in my mobile. Can anyone help me to sort out this situation..?