Why can't I listen to my Audacity project?

I recorded a session using Audacity, but before I could save it it blocked.
I had to reboot the system, so I did so being confident in the fact that Audacity allows recovering past unsaved projects.
I restarted Audacity and it in fact did recover it, I saved it, saved the multiple recordings and closed the application.
This was yesterday. Today I tried to listen to the recording (using audacious.. oh by the way my OS is Ubuntu)
but as it played no sound was to be heard.
So I then opened the project file (.aup extension) with Audacity and I did find all the recordings there, but the graph was a still flat line.
It played but there too was there no sound to be heard.
What must I do to recover the audio to my recordings?

.. desperate…