What happened to the Find My Phone app? it used to work, now it doesn't.

I never had a problem with this app before after using it for years. Tonight i couldn't find my phone. i knew it was in my house but i didn't know where. Find my phone is always helpful and the phone makes a loud sound so i can quickly find it.

But tonight, the app looked different from how it was designed before, it seemed like someone had designed it to be unfriendly to the user. It said words that were irrelevant to finding my phone, it kept saying "locating devices" but my MBP which i was using to run Find my Phone was obviously located, ? i was using Find my Phone on it and my internet connection was fine, as always. i knew my phone was on, it might be asleep but it wasn't powered off. Being asleep was never a problem before.

Finally the app said "All Devices Offline." What does that mean? The MacBook Pro is off line? In what sense? How does it know the phone is "off line?" i don't know what that means. There is an internet connection to my network, and no device is disconnected from the internet or from power. I knew the phone battery was charged.

My last question is, where is the sound option? there has always been a sound option, without it i would not be able to find my phone using this app. What's going on? What happened to the app that used to work to find the phone? All i got from this different looking app was "all devices offline" after a long waste of time while it looked unsuccessfully for devices that were online. Is there a setting that will make this work and provide the 'make a sound' option? or---where is the sound option?

Thanks for any help on this. i don't want to lose another once cool thing about Macs.