In the Mixer:
There is a slider between the channels and the AUX/Main sections.
I think its labeled All; make sure it is up.

In the bottom right set of sliders make sure the left most slider is up.
This is the main output labeled A1 (Audio 1)

If after trying everyone's suggestions it's still quiet, try clicking the FX button on that A1 strip and insert PGPeakLimit.
Move the gain slider up ... better?


I do not work here, but the benefits are still awesome
Make your sound your own!