Octopi.local works, but the IP doens't

What is the problem?
I tried to setup my Octoprint to manage 2 different printers on two instances of octoprint
After the command lines and a reboot I can't reach octoprint through the webbrowser by IP, only by "octopi.local"
Usualy the octoprint instance was reachable through the IP that was shown in my router.
And as a sidenote, in the options where you setup the online test ( Host Port:53 ), this does not work anymore if you test it

What did you already try to solve it?
IP:5000 or IP:5001 won't work
octoprint.local:5000 or octoprint.loca:5001 won't work
The IPv6 Adress from the tips via SSH on the Pi works in the browser, but only for octoprint instance wich was already installed

Logs (syslog, dmesg, ... no logs, no support)

Additional information about your network (Hardware you are trying to connect to, hardware you are trying to connect from, router, access point, used operating systems, ...)

those are the command lines I used in order

sudo su

cd /etc/init.d

sed s/octoprint/octoprint2/ < octoprint | sed s/OctoPrint/OctoPrint2/ | sed s/bin\/octoprint2/bin\/octoprint/ > octoprint2

chmod 755 octoprint2

cd /etc/default

sed s/PORT=5000/PORT=5001/ < octoprint | sed s/HOST= | sed s/$PORT/$PORT\ --basedir\ \/home\/pi\/.octoprint2/ > octoprint2

sudo update-rc.d octoprint2 defaults 99

sudo reboot now

If you have multiple hosts on your network with the same hostname, you're gonna have a bad time.

If they're both named octopi.local then the Avahi service on the second Pi will likely broadcast itself as octopi-2.local instead of what you're expecting it to be.

The final solution, after testing on a fresh install was that my wlan repeater, for some reason, prevented me from reaching to adresses with a port at the end in the browser...
A simple restart of the repeater handled the problem....3h of searching for that...