Snap.as photos won't upload via Firefox (Android 10)

I’ve had this issue for about two months now, and it might be because I am pulling the photos from Simple Gallery (a FOSS photo gallery app), but when I tap the photo to be uploaded, it shows me the “upload progress bar”, but it doesn’t upload. Just wondering if anyone else is experiencing this?

I can confirm that image upload on snap.as doesn’t work with Firefox on Android. (It’s Android 8 here.)