Acceptance Ratio Low
Carefully select you images before submitting!
If you are not sure, start with a small number and see which ones are accepted and which ones are rejected.
Don't make my same mistake at the very beginning by submitting at once hundreds of pictures which have been feeding your folder for years. If you do so, the risk is to start with a very low acceptance ratio, which will be very difficult to increase, apart from wasting a lot of time writing keywords, etc... for images which will be rejected.
My example: I submitted in the first month only 240 images, of which only 60 were accepted. Result: I started with a 25% acceptance ratio. I learnt the lesson and started to get more images accepted than rejected until I reached about 70-80% acceptance ratio on a monthly basis but the first months still penalize me by keeping my total acceptance ratio low. With 444 images on line I am only now close to reach a 50% acceptance ratio, which will eventually enable me to download and submit more pictures per day.