I am pretty sure the message 'DO NOT BOARD - CONTACT US TSA/CBP' means 'DO NOT BOARD - CONTACT US TSA/CBP.'
It might be an immigration issue, and they were not willing to let you enter into the US anymore, despise your B1 visa.
Or it can be a safety issue, and they thought that for whatever reason you are a risk for air transportation. That is, your name is in the no fly list.