I haven't heard of that happening to anyone else, but here are some ideas:
The button can be finicky so if you didn't test it yourself before pressing the button on the speaker, it's possible that it didn't work because of the way they pushed it.
That's not an excuse, a doorbell button should just work no matter how it's pressed, but it's a common problem with this device.
If it happens again, you should try the button yourself and if it doesn't work, then try the doorbell button in the mobile app. If the physical button doesn't work, but the one int he mobile app does, you'll know that the device is fine, it's the button that stops responding.
If it's been happening a lot lately, it's possible the battery is getting low. I wrote two of the device handlers for this doorbell, but I'm not sure if they report a low battery properly because I haven't had any batteries get low enough to test it.
You could also try performing a factor reset on the device. To do this, you need to unpair the device and then hold the button on the speaker for at least 20 seconds. I've done this multiple times and it's never deleted my custom sound files, but it's probably still a good idea to back them up first.
*** Please don't post the same question to multiple topics..