Can't say for sure what happened with yours, but I do know that with normal meringues, everything you use, bowls/whisk, everything, must be very clean and dry. No residue of any oils at all. And not even the tiniest bit of yolk in the whites or it won't work.Hmmm...My whites didnt stiffen, I mixed for ages lol and added shed loads of sweetner, but still nothing. I ended up blending them with the yolks and making lovely syn free pancakes instead.
Still not sure what I did wrong, apart from the cream of tartar bit!