I have had the Turris Mox Classic lying around for quite a while, for a couple of reasons I never got around to set it up. I have finally given it a try but I can’t access the router in my browser for the start-up wizard.
Is your PC with that you try to access your MOX connected to any other network (e.g. via Wi-Fi or another ethernet cable)?
I had similar issues and those stopped when I turned of Wi-Fi of my laptop