Hello Mike,
The DisplayLink Manager software needs and works in tandem with a DisplayLink chip in the docking station.
This dock model doesn't look like it is featuring our technology and that's why you don't get a prompt as there is no chip detected. Therefore, installing the app has no function.
I can only suggest you replace your dock with a dock featuring Synaptics' DisplayLink technology so you can get more than one external display on this machine.
We have a page with a selection of products. If you have one or several preferred brands, let me know and I can look at a suitable product in their portfolio.
Regards,
Alban