This is a configuration issue with matplotlib, the library that QIIME uses for generating plots. You might want to work with your system administrator on this, as I’m not sure if there is a specific reason for this configuration. Your current matplotlib backend is set to qt4agg, which requires there to be an active display, but you don’t have an active display (as indicated by there being no result when you called echo $DISPLAY).
To get around this, you should first check if you have a matplotlibrc file. You can do this by running:
python -c “import matplotlib; print(matplotlib.matplotlib_fname())”
If that returns a filepath, you’ll want to look for a line in that file that contains this:
backend : qt4agg
I would created a backup of that file, and then (in the original copy) replace that line with:
backend : agg
If you don’t already have a matplotlibrc file, you can create one at $HOME/.matplotlib/matplotlibrc. That file should contain only the line:
backend : agg
As I mentioned, you might want to talk with your system administrator about this before making any changes.
Sorry for the trouble - I realize this is a bit of a complicated fix, but it does seem to be a server/matplotlib configuration issue, not an issue that is specific to QIIME.
If you could get back to me to let me know if that works, that would be very useful in case other users run into this in the future.