I've managed to reproduce the issue on Win2k8R2. It's coming from ImageMagick not being installed/configured correctly.
These are the steps I took to fix the issue:
Go out and install the latest version of ImageMagick
After running the installer make sure that you close the command prompt from which you are running NodeBB.
Open a new command prompt and rerun node app.js
The problem should be fixed!
So, I just tested leaving the allowed filetypes-field blank (ergo allowing everything) and that worked. The mov-file gets uploaded flawlessly.
But interestingly the response is:
Adding just the mov extension to the allowed file-extensions blocks it again.
Now the response suggests to me somehow, that nodebb is converting the uploaded file to a .qt-file.
So I just added the qt-extension to the allowed files and it works.
It's really weird behavior, but I found a solution. Thanks for participating everyone!
Need to add localStorage to it, but also an option to re-enable in the user settings in case you accidentally closed it and actually do want it activated.
In any case, noticed OP is on an iPad, so made some changes that might work for him