FileTypeGroup Icon

Could someone tell me what a yellow triangle with a black exclamation mark above the image I use as an icon in my FileTypeGroup means?

Thank you

There is a ToolTip if you fly over it. I have the same and for me it’s because I don’t fill the 8 bit icon.

I filled all the images. I haven’t filled the masks (because I don’t exactly know what they are for). Might be it?