According to the Twitch’s Terms of Service, they do not allow “Nudity and sexually explicit content or activities, such as pornography, sexual acts or intercourse, and sexual services.”
For what it’s worth, Impact Wrestling aired a segment on this week’s broadcast that featured Rob Van Dam, Katie Forbes, and another woman which featured blurred nudity, whipped cream and the idea that they were having sex. That may be the reason for the ban.
The first bans on Twitch are usually not permanent. There is no word as of this writing on how long their ban is for:
— StreamerBans (@StreamerBans) January 16, 2020