Can't drag windows to second external monitor

[VinylChef]

Hi,

I have:

MacBook Pro M1 Max with DisplayLink software installed
i-tec CATRIPLEDOCKPRO docking hub
2 x LG 27G640A-B UltraGear™ G6 27-inch 300Hz QHD IPS Gaming Monitor

Both monitors are attached to the rear of the dock by HDMI.
The MacBook is connected to the powered USB-C port and is sending a signal to both monitors just fine.

Both monitors are showing wallpaper and the icons at the top of the screen.

Both displays are appearing in Systems Settings > Displays.
Both displays are appearing in the DisplayLink tab and they both show a red border when I hover my cursor over them.

However, when I run my cursor across the border of my MacBook it runs into one of the external monitors but not the other, so I can only effectively use one.

Interestingly, when I click on Finder, it opens a Finder window in the non-responsive monitor but I can't access it with my cursor.

Can you help me to solve this problem so I can use both monitors?

Many thanks,

David