Volumio App. On iPad Stops Seeing Volumio

Hello folks, I’m using Volumio on a Raspberry Pi 4 with music on an attached HD, connected to the router with an ethernet cable. When first starting up, the app. on my iPad works fine, but after a while it stops seeing the Pi, no matter how long I wait. Same with trying to access via a web browser.

I’m wondering if after a time this goes to sleep? The only way to re-access it is to switch the Pi off & reboot. It’s a real nuisance so any help in curing this would be much appreciated!
Volumio 3 Issues?

Please see: Volumio 3 issues: hints and solutions before posting a new issue.
(You’ll need to cut and paste the link)

----------------------------- Delete here & above before posting below -----------------