Stuck in Back lever position

Hi just been trying to nail the back lever on the rings. But have a major problem. I remain tense and everything and after i turn upside down and put my feet over so I begin my decend into the back lever I seem to get stuck. My upper body cant seem to get upright and cant move my head upwards to become straight. I need to upload a video to see because the description is a bit weird. Can it be due to having poor shoulder and chest flexibility?

Probably it's more the orientation of being upside down. Some people sometimes think they are horizontal and they can be barely off vertical.