Look I am not IT savy other than learning by trial and error. There is a app named “Fing” that you can download from the App Store - this app will show you IP addresses of all your devices on the network or your should be able to obtain this information from your router that was provided by your broadband provider (in my case I replaced the router with commercial grade router namely “Ruckus” unleashed model to eliminate any dropouts in a general sense for other devices in our household and also have switch boxes as most of my devices including say for example security cameras etc are done via cabling)
If your Devialet is properly configured, in that, after the factory settings reboot - your Dev will appear on either the Fing app or your router or via windows enquiry with a IP address that you simply type in on the browser either in a PC or Mac - if it does not appear (usually will state the word “Configuring” - I would then suggest doing a hard reboot (unplugging the power supply) reloading the latest firmware and going through the process (remember to take out your SD Config card when you do the firmware upgrade). In terms setting static iP addresses etc that also can be done on the router - for example I have assigned static IP addresses to my Synology NAS server, ROCK, Devialet etc. I do not know your network architecture nor do I know your configuration for your router settings therefore I am incompetent to guide you here - also I am not tech savvy so I maybe doing things the long way so perhaps you are better off seeking some advice from a IT Network person.
It is really important to understand your network so that the Dev (which really is a dumb computer) can talk to the device your loaded your Roon software. One of the reasons I went the stand alone NUC/ ROCK solution was to remove issues I was having within the Microsoft platform (I think apple has some issues as well).
Anyways I know it is annoying as Dev does not provide IT support but I do think that is an unrealistic expectation - My view is that people like me need to be somewhat IT aware if I go down the path of purchasing a Devialet style network device and I do think the guys at Devialet are subjected unfair criticism when they are rolling out an upgrade for gratis - I think the guys at Dev are working hard to understand and work out the variables in different networks and make allowances as much as they can - I reckon it would be a nightmare coming up various permutations as Dev engineer - therefore I think the beta testing program that they rolled out is the only way to go in my view so that they gather the feedback and work on fixes which they have been doing (and on some occasions I have contacted Olivier the engineer directly via email and he was very helpful with advice akin to Danny here at this forum). I really hope you can find the fix and tell us about it. Good Luck.