I use SAI, but I've never encountered this problem before. Or maybe I have a long time ago, but I just forgot about it? 
Anyway, as for a possible solution... What if your file is corrupted? Did a power outage happen while you were working on it? Did you use the cut command and it got interrupted? Or a virus of some sort? Because that may be the reason why it's not opening. If not, then maybe you should try uninstalling SAI and installing it again. Or you can try transferring the SAI app to another PC/laptop and try to open the canvas there to see if it works.
I hope this helps! If not, I'm sorry 