I just tried that without success (yes, I made sure to restart NodeBB). Also, the developer mode doesn't fix the problem (contrary to what's stated in the linked thread).
Okay, so it must be something else.
I'm not sure if this has anything to do with the issue, but I had a few errors while setting up NodeBB initially, which I had to address.
Wow, um, big red flag there. How did you install NodeBB in the first place? It may be wise to start from scratch and reinstall with correct permissions from the get-go. You absolutely should not use sudo to install or run NodeBB. The only installation-related things you need root access for are nginx configuration and maybe changing directory privileges before installing NodeBB.
What OS are you installing NodeBB on? Are you following any tutorials or instructions?
My OS is Ubuntu 18.04 and I followed a documentation from your website. I started from scratch and it's running fine now! I assume the guide I used must have been outdated, which led to some errors. I must say that it might make sense to clean up the documentary and make sure that only one version of the installation guide for every OS exists to avoid confusion.