How do I check if my png file has alpha and remove the alpha?

If using Export/Quick Export, even if the file is flattened, double check that the transparency checkbox is not active:

It is possible to check for transparency in the PNG files using other software, however the expedient approach would be to simply re-save all PNG files with transparency off.

This is the file I'm working with. I'm trying to upload it to Apple's App Store Connect for my app, and I get an error saying it has an alpha or a transparency, but I can't find either one in it to remove it.

Here are the layers, channels and paths.