Ok, is it possible for you to send me your blocks, all of your properties and your design layout?
To send your blocks please right click on the blank area in your blocks page, then download blocks screenshot.
To send my your properties please get a screenshot of the area that properties exist (if you’re on a mac please use the tool named “Grab”. For Windows please use “Snipping Tool” (as I remember)).
To send my your design layout please reproduce the steps I described to you for the properties.
Could you show us what the error is?
Make sure that the icon is .png or .jpg file format and I would recommend that the resolution is no bigger than 96x96.
@TurboProgramming I don’t think blocks are needed as it seems the problem occured after setting the icon.
As Conor said, you should use an icon that is .png or .jpg and it should not be bigger than 96x96. But, in all of my apps, I use a PNG icon with a resolution of 512x512 and it works perfectly.