I recently had a huge issue connecting to zone minder, only one computer was able to connect to the web service. I also have a couple of video wall 4k displays where the video footage is being live displayed.
Because of the video wall displays I knew the issue was not with Zoneminder, PHP, Mysql, or any other component responsible for rendering the mjpeg displays. What I eventually found via the terminal was a obscure entry in the syslog.
Running while refreshing the ZM server http://172.18.1.150/zm/ :-
tail -f /var/log/syslog
I was able to see a error in the syslog, No skin found for ”. This in turn led me to set the theme in the http webrequest by instead of going to http://172.18.1.150/zm/. You will need to append ?skin=classic
The root cause of this issue is this. Zoneminder can’t find the default skin ”. This is because in your options, there is no default skin set. Why it continues to work on some browsers is because the skin name is also saved to a cookie. zmSkin.
So when you goto the URI with ?skin=classic. this tells zone minder what skin you want to use. Open options and set the SKIN_DEFAULT parameter to classic. and you should not see this issue again.