I guess it was rejected for 'technical issues'. The composition is not good. The horizon is dividing the picture in half. Secondly, it looks like you have added filters to it to make it more pink. It's not a good idea for stock. Buyers will want to add their own effect, so it is best to leave it more natural.
Have a read of this. It's a brief guide on image quality:
...and this from Adobe about how to create better photos: