Can't upload app for first time: At least one screen image is required.

I get a "At least one screen image is required." error in Screen imaged section of in step 2 of https://apps.garmin.com/en-US/developer/upload when trying to upload an app for the first time.

I have added 4 images, so don't understand what the problem is.

Is the 150KB limit per image, or for all 5? Have tried images where the total i below 150KB so guess it is not this.

I'm using Firefox and have updated to latest ver 119.0.1 in case out of date browser was the issue

Any Ideas what I am doing wrong?