You did the hard part already. So when you setup StartOS through start.local, that “start.local” will go away and provide you with a new .local URL that looks like https://[random adjective]-[random noun].local
Did you write that down anywhere or know how to find the IP address of your new server?
I am having the same problem. So I then connected the server to monitor, set a password for it but still cannot access the start.local address, to install the required applications on my MAC laptop.
The start.local address is only valid during the initial setup. Sounds like you’re past that part. If you don’t have the config page you were offered during the setup, you can find your host name under System>Insights>About>LAN.