Hi Mat! Welcome to RSW!
I'm not sure what's going wrong with your client, but let's see if we can figure it out. It shouldn't be a compatibility issue; the client is compiled for Windows 10 and should run fine on any Windows 10 machine.
One possibility is that somehow the client database is corrupt. That would be really weird if you've only just installed it for the first time, but weird things happen sometimes, I guess. If this is the case, resetting the client database should clear it up. In fact, since this is a new install, let's reset the entire RSW save folder. To do this, type %appdata% in the Windows search bar. This should take you to the folder C:\Users\<your name>\AppData\Roaming (note that AppData and Roaming are both hidden folders, and you can't navigate to them the usual way). In this folder you'll see a folder named RSW; click on this and then hit the Delete key to delete the folder. Then try to launch the RSW client again and see if it loads (it should prompt you for a username and password).
Another possibility that comes to mind is that maybe some firewall software (like Norton or whatever) is blocking the client's attempt to communicate to the game server, and causing it to crash as soon as it makes the attempt. Make sure you have configured your firewall software to allow any network communications by rsw_client.exe.
If you can't get anywhere with either of these, let's try some diagnostic experiments. First, try right-clicking on the RSW Client icon and selecting "Run as Administrator". Maybe that will make a difference?
If that doesn't help, let's try starting up in offline mode. In the Windows "Run" dialog, type the following command:
The easiest way to do this is to click the "SELECT ALL" button above, then hit Control-C to copy the command to the clipboard, then Windows-R to bring up the Run dialog, and Control-V to paste the command, then hit Enter to run it.
This should launch the RSW client in "offline" mode, where it won't attempt to connect to the server. If it launches and doesn't crash, then you can try hitting the F5 key (or picking File | Download Games from the menu) and clicking Yes when it asks you if you want to connect. If *that* makes it crash, then we have at least proven that it's crashing whenever it tries to communicate to the server, and we can proceed from there.
David