how can find who banned me ?
No way. Unless the person who banned you responds to you.
I can also assume that Malwarebytes may well have complained to theymos about selling their license keys on our forum. Selling their license keys is prohibited by the Malwarebytes Software License Agreement. Therefore, it's quite possible that theymos itself banned those who were selling keys and deleted their threads
Quote from: https://www.malwarebytes.com/eula
If you purchased a license to the Software from Malwarebytes or from a Malwarebytes authorized reseller, then upon payment of the associated fees, as and when such fees become due, and conditioned upon your compliance with the terms and conditions of this Agreement, Malwarebytes grants you a non-exclusive and non-transferable license to Execute the number of copies of the Software for which you have paid solely in executable form on the corresponding number of Devices owned or used by you.