Rush Street Capital - Bought my business but didn't pay me all the money Chicago IL

I sold my business to Rush Street Capital and their various named LLC's but the principal for all of their named businesses and LLC is Phil Kane. The business was sold on 10/21/2022. They stopped all payments after February of 2024. To this day, they still owe me hundreds of thousand dollars. On July 16th of 2024, I received a letter from a law firm located in Washington,DC. The letter informed me that they are in default with their bank, and therfor, I can not collect any money until they pay the bank first. These people are as unethical as you can find. Everything they do is shrouded in LLC names so they can never be liable themselves. Buyer beware: do not do any business with any of these companies associated with Phil Kane, Rush Stree Capital, Harmonic Heating and Official Heating.