You can always contact the reddit team and if your account is suspended wrongly, it would definitely be reinstated.

Also important to note that if you didn't post a lot, many subs will auto-remove content from low karma users. So it's possible to have misidentified a global shadow ban with a few subreddit's low karma filter. One of my spammer adversaries regularly games FreeKarma4U and a specific star wars game subreddit until they figure out our low karma filter threshold then they go nuts with the spam.