Think I see the problem. In the drop down menu, "WLINK" is prefilled as the recipient. Instead of using the drop down option, manually type "WLNK-1" in the to field. Then type anything in the message field and send the message. The Winlink system should respond with something like "Login [176:]" which starts the connection. Details on logging in and reading messages in the video link above.
73, de KM4ACK
km4ack