I don't know what is going on. I've created many transparent PNG's using Illustrator, but today nearly every attempt has resulted in the final image having a solid black background instead of transparent.
 
I export selection, check the cog and transparency is turned on. Out of curiosity I repeated the process but selected White in the cog and it still saved a black background.
 
I've created new projectd, made the most basic shape, and after exporting, the same thing happens.
 
I checked to see if there was any updates. There was a minor one. I updated, and when I tried to export after the update the background was finally transparent.
 
HOWEVER!!!!
 
I had to update a logo, opened Illustrator up again and did my thing and when I exported the PNG the same thing happened. I'm back to seeing a black background. Thinking, have I doubled up Illustrator?? So I close Illustrator and open it from the Creative Cloud app. Nope that's not it.
 
Help....