I tried adding new relic package into my nodeBB install by adding
after removing the new relic agent from app.js its working fine again.
I just wanted to let other nodeBB forum administrators to know about this issue if they face same problem.
Thanks for the reply.
I had misunderstanding how this plugin works, now I got it.
It works now 🙂
Just for other users if they see this topic in the future: You should go to each Category you created before or create after that, click on Subscribe green button and the plugin should work for you like me.
For example in my website I have 3 categories called Q/A, Free Discussion and Announcements. I should subscribe in all these three and then just wait for another user to create topic.