I am trying to play the Space Station 13 server, Paradise Station.

However, whenever I try to join, I get the error "Encountered an Improper Argument" and cannot click any buttons or continue.

I can play other BYOND games and SS13 servers but not this one. What is this error and how do I fix it?

I am running on Windows 7, have uninstalled and reinstalled, updated drivers and DirectX. I'm not sure what else to do.
Unfortunately this particular error message is very difficult to diagnose, but one of the known problems is very long path names. Is your BYOND user data path by any chance in a very long path?

You can find the path if you go to the pager and open Preferences | Advanced. That will tell you where your user data is. I don't recall if Windows 7 would be the same as Windows 10 in this regard, but in Windows 10 the path is typically C:\Users\username\Documents\BYOND.