At the very least you'll need to provide what is shown under 'Show Details'.
Extra screenshots showing the existing connection etc would be helpful.
I suspect your best course of action will be to create a case with Tableau Support though as there really isn't enough information here to help you.
Without more context on the details for the connection you're trying to add and the steps you're actually taking, there isn't really much help I can provide. From that screenshot I can't tell where you got to in the process of creating a connection, what details were used, what version the server is, if you used custom sql etc.
It might be a better option for you to create a case with Tableau Support.