What version of Zoneminder are you using (there were issues using 1.31.1 with OH)? I am using 1.30.4 and everything is working fine. Have you restarted OH after the Zoneminder binding installation? And have you set Zoneminder logging to debug and looked into the logs to see if there are errors? Can you access the API with curl? Read through this and see if it may be similar to your issue…
