From your post it isn’t even clear what TrueNAS edition and version you have installed.
When I recently installed TrueNAS Scale 24.10.1, the console showed me the network configuration and gave me an option to change it. So take a look at that by connecting a monitor (and if necessary) a keyboard to your old computer and look at what IP address TrueNAS is using. That’s the IP address you will need to connect to in order to reach the web interface.
As a general rule you should ensure that this IP address is stable by one of the following methods:
Configure it as “static” in the TrueNAS console itself, but pick an IP Address that is within the subnet of your network, but outside the DHCP range (which is the range of IP adresses that your router dynamically gives out for that subnet).
Configure it as dynamic (DHCP) in the TrueNAS console, but define a static IP address within your router for the MAC address that is associated with the network interface of your old computer. Once again that address should also be within the subnet of your network, but outside the DHCP range.
Example: If your router has the local ip address 192.168.1.1, then your subnet uses ip addresses from 192.168.1.1 to 192.168.1.255. Your router will have a configurable range of ip addresses it can give out dynamically, e.g. 192.168.168.32 to 192.168.1.254.
In that example you could e.g. use the IP address 192.168.1.20 as a stable IP address for your TrueNAS system (assuming of course it isn’t already used by another device.)
Are you getting to the console window on your install? What is your current networks setup, DHCP? It helps if you list the hardware details and the OS version.
I will check which version it is, but first here are the hardware facts:
Desktop PC:
Mainboard: Pegatron M2N78-LA
CPU: Intel® Pentium® D 925 3 GHz (2 cores)
Ram: 16 GB DDR-3
Graphiccard: MSI GT 710 2GD3H LP - 2GB (low power consumption and passive cooling)
One HDD-Drive with 250 GB for the system and two 1TB HDDs as storage. Maybe a third 1TB will be added.
I also put in a better power supply unit with 450 W instead of the original 300W.
Switch: Netgear GS108
Maybe I have to say that I am complete new to this topic (NAS) and I am also looking for a suitable handbook for TrueNas. Is there one on the market which you prefer? (English or German)
Do you have a router connected to your Netgear GS108 switch? The switch doesn’t assign IP addresses by itself. What device is serving DHCP? Are you manually assigning addresses on your network?
Did your TrueNAS computer work on the network before you loaded the OS? I am wondering if the network card was working under Windows or other OS.
But this switch is connected to a router, correct?
So what does this screen show for you?
From what other system (“client system”) did you try to connect to the TrueNAS system and is that “client system” in the same local network, that is connected to the same switch and/or router?
And what did you enter in the browser of that “client system” to try to connect to your TrueNAS system?