Did my tablet ever start the encryption process?

Before I went to bed yesterday I switched on encryption on my Kindle Fire HD (Cyanogen KitKat ROM), and ended up seeing this screen:

Looking around, apparently it's supposed to also have the text Encrypting Tablet and a percentage of progress.

When I lock the screen and turn it back on, I do not see the status bar and it asks me for my PIN, of which when entered it goes back to the same screen as before.

It looks to me as if it never actually started the encryption process, but I'm still wary about rebooting it and losing my data/corrupting the tablet.

Would it be safe in this instance to reboot the tablet, and what would cause the encryption process to 'hang' like this?

As aforementioned the tablet is a Kindle Fire HD with a Cyanogenmod KitKat ROM, and has only 300MB out of 14GB storage capacity left.

Might the low amount of available storage cause this?