If you want to use two Cam Links on one computer at the same time, your computer will need to have two separate USB 3.0 Root Hubs or Host Controllers.
Not every Desktop computer has two separate USB 3.0 Root Hubs.
Many Laptop computers do not have two separate USB 3.0 Root Hubs.
The following article discussed where you can find out how many USB 3.0 Root Hubs your computer has.
PCs and USB 3.0 Root Hubs
https://www.uwe-sieber.de/usbtreeview_e.html
Macs and USB 3.0 Root Hubs
You can use the System Information application on your Mac to find how how many USB Root Hubs are installed, and whether they use USB 2.0 or USB 3.0.
Here is a screenshot showing a Mac with two separate USB 3.0 Root Hubs and a Cam Link attached to each one:
Here is a screenshot showing a Mac with two separate USB 3.0 Root Hubs, but two Cam Links are attached to only one USB 3.0 Root Hub. This will cause problems, or not work at all:
Here is a screenshot showing a Mac with only one USB 3.0 Root Hub. Only one Cam Link can be attached:
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