Thanks for your persistence. I still can’t get it working.
I added my MBP to the list of fixed IP addresses on my router.
In the desktop app settings it says Roon ARC can securely see the Roon Server.
Opening the app on my iPhone I just get the spinning circle and a message saying it is taking longer than usual to find the server and I m right want to check the network settings and firewall.
As far as I k now, I’m not using a firewall - I don’t remember buying/installing one.
Are you attempting this using Wi-Fi or 4G? Furthermore, if you’re using a VPN or content blocker on the iPhone, turn these off. I’d also turn off the iPhone Wi-Fi while testing at home, and make sure the MacBook isn’t sleeping.
MBP up and running, with Roon open.
No vpn or firewall on iPhone.
Wifi disabled on iPhone.
Still can’t connect.
Hi Daniel
I have 2 days left. Is it too late to get an extension?
Not at all, @Stephen_Bavis. Thanks for keeping an eye on your remaining trial days. Our team has just extended it.
Thank you for working with our technical team 
Every laptop, including your MacBook Pro, can connect to a network via wire (Ethernet) and wireless. It can have 2 different connections simultaneously. During this phase, try to have only one enabled and in use. In practice, I would recommend your MBP running Roon be running via wire (Ethernet) only, and that you should disable WiFi. If you need help with that, let the community know and we will help more!
My MBP does not have an ethernet port and I don’t have a hub to provide one, so I can only connect by wifi. So I don’t have the problem of conflicting connections.
I am still none the wiser as to why my MBP can see the server but my iPhone can’t.
Go into network settings on both devices, and share the IP address assigned to each.
Hi @Stephen_Bavis,
Just for due diligence - did you try clearing the cookies in Settings → Safari on the affected iPhone? What about disabling content blockers?
iPhone IP is 192.168.0.40
MBP IP is 192.168.0.26
To answer Connor, I do not have any extensions active in Safari on the phone.
Hi @Stephen_Bavis,
Try clearing the Cookies in Settings, specifically. If there is a stored bad cookie interfering with OAuth, it will break the single-sign-on process and interfere login.