Manually creating a new s2 member customer using their existing stripe account information

Does anyone know how to take existing stripe account information for a customer (cus # and sub #) and create a new s2 member account on their website that fully integrates and will allow you to display an accurate EOT or next payment due date for them?

I transferred the cus # and sub # over but it’s still not integrated so I’m missing a piece of the puzzle.

Any suggestions would be appreciated!