And now I thought I'd try it with my device. It's on my work wifi and on mobile data. "Play a sound" works. But it still insists "Can't reach device" and won

And now I thought I'd try it with my device. It's on my work wifi and on mobile data. "Play a sound" works. But it still insists "Can't reach device" and won't tell me where it is. What am I missing? "Find my device" is toggled on in the settings.