If you start a Meridian 218 Before your DHCP-router then the 218 creates a fixed IP-address (like 169.254.30.22). This IP-address is not detected by Roon.
That is because that IP is unlikely to be within the same subnet as your LAN.
What is the subnet of your LAN?
Some devices let you change the default IP, I believe the 218 does. Have you tried reconfiguring?
What’s the back story on why are you powering up the 218 when the DHCP server is down?
For network stability it’s imperative that the DHCP server is running first. Though most devices will timeout a re-request for a DHCP assigned address eventually.
So if the 218 is rebooted when you router/dhcp server is booted and available what happens?
The other resolution is to assign a fixed IP address on your subnet but outside your dhcp pool range.
Now I’m a little bit confused. Today the missing 218 showed up in Roon with the same Ip-address as yesterday.
The only thing that has happened is an Windows10 update.
@Ratbert I do prefer dynamic IP-addresses.
@Carl My home network is switched off most of the time. I only use the network 1-2 hours per day.
169.254.?.? is the ip address that will be assigned to your device if 1 - your device is set DHCP and 2 - your device is not on a network.
Upon bootup, DHCP will scan a network for subnets. If you are part of a network when booting up, then DHCP will assign a Network Associated IP Address. If you are not on a network then it still has to assign an IP and that will start with 169.254.?.? and therefore Roon will not see this device.
If your router has finished powering up completely, then rebooting the Meridian device should grab a associated network address if you have this device set to DHCP.