I solved my problem...
I did like this:
when logged in in the Pi with terminal or Putty i wrote
service octoscreen status
Then i saw that Active: sayed Activating, but it should say Active (Running)
I then went in to:
sudo nano /etc/rc.local
scrolled all the way down in this list and before the last exit 0
systemctl start octoscreen
pressed control X, then Y then Enter to save
This might be enough to fix the problem, but in my case it was not, but after doing this i reinstalled
by pasting in following:
sudo apt-get install libgtk-3-0 xserver-xorg xinit x11-xserver-utils
Then after running that i pasted in:
sudo dpkg -i octoscreen_2.5-1_armhf.deb
Now OctoScreen works, hope this is help for anyone else here.