I do feel and understand your frustration. I am seeing more and more of these kinds of posts here and on social media. It is absurd and I don't see how, even legally, the platform can immediately suspend you yet refuse to disclose the reason.
Unfortunately, based on other posts, the problem could be a previous guest lodged a complaint about you. Might have claimed you were racist, that there was some type of safety violation in your home, that someone associated with your account was charged with a misdemeanor years ago. These are only examples other hosts gave when faced with the same situation and may not reflect what happened in your case.
Try calling AirBnb back and ask to speak directly to an ambassador. Don't expect any decision reversals, but press your concerns. Tweet Chesky, go post on FaceBook. Find a copy of AirBnb's terms of agreement that you inadvertently agreed to when you set up your account. If you have a friend of a friend that knows an attorney, speak to them. Hopefully, the suspension will turn out to be temporary. I do wish this resolves favorably for you.