I am somehow unable to connect to Volumio from my phone.
Either using the webbrowser or the app.
My phone is on the same subnet as all my devices and computers, and connecting to it from my laptop or desktop is no problem at all.
It just times out on the phone.
Also, this is with both the DNS name as well as the IP address.
Not that it should matter, but tested either way.
What could cause this?
Do you see the volumio hotspot?
Can you connect to that and check the network config or finish network setup?
After installation I used a monitor/keyboard/mouse to do the initial configuration.
Volumio Hotspot is disabled.
As I have configured the network setup, what do you want me to finish?
Volumio is designed to run headless and be managed by a web browser or phone app.
I know that. That is why I disabled the HDMI, which is enabled by default afaik.
Then why this?
“I used a monitor/keyboard/mouse to do the initial configuration.”
Because there is nothing wrong with that?
I hooked it up to my monitor/keyboard/mouse, did the configuration and then set the HDMI option to Disabled.
But still, that has nothing to do with my issue.
If you can connect to the webpage from laptop and desktop, that show’s the system is working, therefore it is probably a problem with your wifi/phone/app.
Have you tried using the web browser on your phone to see if that works?
Yeah, not working either. That is what surprised me most.
As it is working from the desktop or laptop which are all on the same subnet.
Do you use DHCP or Static IP Address’s, if static do you have two devices using the same IP Address?
Whichever you use, try the other, no reason for it to make a difference. but you never know 
I used DHCP at first but had issues with that, which I address to config part of Volumio.
See Networking is a mess
So I use static now, and that has other issues (see link above).
But with that I can at least access the webpage just fine from the laptop and desktop.
There is nothing using that IP address in my network.
Everything separated in IP blocks. I use 10.42.0.0/16 at home and computers like my desktop, laptop and things like my CoreELEC and this Volumio VIM3L’s are in the 10.42.60.x range.
Even when using DHCP the Volumio has it’s address fixed to that since I use the DNS record to read the IP address. You can do that with the fixed-address option.
My phone receives a lease from the DHCP pool, which is 10.42.200.1 to 10.42.200.250 (just realized .50 would be large enough, but not intervening in any way) .
I could try to give my phone a lease in the 10.42.60.x range too just to test it. But if that solves it, something weird is going on.
Something is definitely wrong in Volumio. I can’t see it any other way.
After setting the phone to 10.42.60.10 via a fixed DHCP lease, it can now access Volumio (on 10.42.60.5) via the app immediately.
I will try it with an address in the different block, just to be sure.
Giving the phone the address 10.42.70.10 and it can’t find Volumio anymore.
The app will simply keep “Searching for devices”.
Switching it back to 10.42.60.10 and the app finds Volumio again straight away.
Depending on the subnet mask, the 10.42.70.10 could be on a different network to 10.42.60.10
A class C mask, 255.255.255.0 says those are two different networks.
Yup, except I already mentioned a couple of times I use a /16 subnet, or 255.255.0.0.
So both 10.42.60.x and 10.42.70.x fall in the 10.42.x.x with 255.255.0.0. netmask.