As described here - https://www.reddit.com/r/shadowbanned - message the admins.

But from https://www.reddit.com/wiki/reddiquette:

"Feel free to post links to your own content (within reason). But if that's all you ever post, or it always seems to get voted down, take a good hard look in the mirror — you just might be a spammer. A widely used rule of thumb is the 9:1 ratio, i.e. only 1 out of every 10 of your submissions should be your own content."

and do feel free to remind them that

Shadowbans are meant for spammers, not real users according to reddit's CEO /u/spez - https://www.reddit.com/r/IAmA/comments/3cxedn/i_am_steve_huf...

Good luck.