I have looked at the Amazon web page that you shared. It did not say anything about compatibility with Robotis servos. So that is probably is the problem. Robotis servos run at half-duplex. You’ll need to get the U2D2 module.
For first time setup, you also need to connect your servos one-by-one and assign unique IDs to each unit. The default ID of 1 will produce collisions when multiple servos are connected, and will prevent the servos from being detected.
Thanks for the replies. I believe the controller I am using should be compatible, as I am following this build GitHub - AlexanderKoch-Koch/low_cost_robot where most people did not run into issues using exactly that hardware. There is one user reporting that he had tried 2 identical waveshare controllers, one had the same issue I am seeing and one worked as expected, so I may just have a bad controller.
I am testing each servo one by one.
I will try with another waveshare controller, if if I still see issue will try using u2d2.