Hi and welcome to Digi Forums.
I would suggest to check our self-service documentation for the TransPort WR21 and see if one of the examples would fit the way to connect to your equipment here: https://www.digi.com/support/productdetail?pid=5499&type=documentation
For any further help or investigation on that issue, please review our support options on our website: https://www.digi.com/support and mail our support team at tech.support@digi.com
Thank you
Regards
Alex
Digi Technical Support Engineer