Uploading a passport photo sounds simple until the application flags it as invalid. That happened during my own application, and figuring out the Morocco eVisa Photo Requirements turned out to be the fix that made the second attempt go through without a hitch.
Quick notes worth remembering:

Photo must be recent, taken within the last six months, with sharp clarity and natural colouring
Background needs to stay plain white, no shadows, patterns, or busy walls behind you
Face forward with a neutral expression, no smiling, no sunglasses, no tinted lenses
Head coverings for religious reasons are fine as long as the full face stays visible
Beards or unique marks like scars should look exactly as they do currently

 
Getting these small details right the first time saves everyone a frustrating resubmission later.