Not turn on, as in "unable to re-flash while holding R button?". You might have bricked it.
Did you use an older Fat32 formatted SD card? (You should use a low capacity sd card for reflashing. 1 or 2 GB ones)
I do not have a Caanoo myself. But by now, the battery could be crappy. Did you try to just leave it charging a few hours. Does the caanoo get hot?
Also try this if you have a cable:
Plug it on your PC with your USB cable and turn it on. Does it come up in USB-media mode?
And if it is really bricked, then maybe it can be revived by EvilDragon, you would need to send it to the shop (but ask first if he has the devkit for it that connects to the GPIO pins to reflash in that way). Not sure.
Maybe if you dig more in the forums you can find other methods:
pyra-handheld.com