Volumio with Raspberry Pi loses connection

Hi all,
I have a Raspberry Pi3 B with a memory stick for the music, and Volumio installed. I use Wifi. If I leave it unused for several hours, it is not accessable anymore. No webinterface, no SSH, no ping.
What can be the reason? What can I do about it? Is it a sleepmode?

Do you have a good quality power supply? I’ve had better luck with all things Pi related by plugging any USB things into a powered hub.

If you have a USB wifi adapter, you could try using that to see if it has any effect (there have been reports of RPi 3 wifi issues for some time. For example, see here).

Thank you for your replies. Currently I use the USB port from a amplifier. I don’t know what the power quality is. Can I somehow check logging or so?
Last night Volumio kept playing music ( with Hiberry DAC+ attached to Raspberry, connected to a amplifier) but it was not reachable over wifi. Not with PING, SSH, Webinterface. It uses the built in wifi of Raspberry. Music was playing flawlessly.
I am also doing some research on the Arch Linux forum. I discovered that: volumio-network.service is disabled. What is it for? Hotspot?