Images being rejected by Adobe stock due to quality issues, that are being accepted by other stock sites.

Hello,

Yes, the lens flare is a problem and a reason for rejection.

Possibly, also the sun flare in the middle of the photo.

This is enough for a quality rejection reason.

You will read different opinions in the contributor forum. 

The first thing I see in your photo is flaring happening on the lower right of the frame, enough to give displeasure at first sight. In a scene like this one, I would take many shots, moving the camera millimeters to place the sun behind branches and flowers, maintain the rays and reduce the flaring. Or just use a tripod to put the camera exactly where I want.  I doubt Getty Images or affiliates would accepted either. I think it’s great you can sell it in other sites, remembering Adobe Stock is a place where clients expect great quality. Keep in mind that in order to get better, you will need to demand a lot more from yourself when you are taking your shots and editing them.

Keep Shooting and enjoy the process!