I tried saving my work as a .sai file but I get a message that says "failed to save canvas". Has anyone else encountered this? What should I do? I can save it as every other file type except .sai.

I tend to get it on occasion when I tried to use the fan-translated English version (only because I needed to make a SAI tutorial in the past, using the English language version,) but I don't get it on the original.

The English may be messier on the "official" version, but I would otherwise recommend it, because I never got that error when I used it. I don't get it at all in the original Japanese version (which is what I use.)

If it persists though, it might actually be a different kind of issue which isn't tied to the translation.

I'd suggest saving it in another filetype first, to reduce the hassle of switching translation versions, or just saving in another location (latter used to fix the issue for me.)

Pretty much everything said! That happens to me quite often as well, I've just started saving everything as .PSDs instead of .SAI files. Much easier. xD I use photoshop to make my art transparent, so saving everything as a .PSD helps me open them in PS right after having them open in SAI! That way I don't have to resave a .SAI file as a .PSD to do it. Hope that makes sense, lol.