"Detect Displays" not working, monitor only mirrors Macbook Pro screen

I have a 2017 MacBook Pro and I want to use a second display. The monitor works fine and the port is now brand new and working (j5create USB-C Triple Display Docking Station). I have used this exact monitor and port before and it worked perfectly, but after a Mac update (don't remember which), it suddenly stopped working. I bought a new port, checked all the cables, restarted, updated, uninstalled and reinstalled the driver, everything. Now, it only mirrors my laptop display. There is no "Arrangement" tab in displays. I click on "Detect Displays" and nothing happens. It knows its connected to something (there is a monitor icon in the top bar), but it can't detect the monitor. What do I do?