I'm fairly new to all of this but I have flashed an old model B with Octoprint and connected it to my home network and printer, and I can see it on my router. When I paste the IP address into my browser I get a 404 error. Any ideas?
What IP address are you using, the IPv4 or the IPv6 type?
And did you add the port number?
I'd try using SSH to connect to the RPi. If that works, it allows a larger number of troubleshooting options.
My guess is that he'/she's been issued an IPv6 IP address and they're trying to use that in their browser without surrounding it by square brackets.
IPV6 is the devil's work !
The devil's work I say !
Seriously. Connect keyboard mouse and monitor to pi
then select normal ip goodness