RDS is a complex service, and things will go wrong. Here are a few tips if you run into problems.
1) Clear your web browser's cache (or try using a different browser on your system). Instructions for various OS/browsers are in the table below:
2) Download a new RDP file (how-to is under "Retrieving an RDP file on this page: https://answers.syr.edu/x/GopDBg).
Updates to individual school's lab environments may require that you get a new RDP file in order to connect properly. Note, this doesn't apply if you're connecting to RDS in your browser.
3) If you're on a Mac, make sure your Remote Desktop app is fully up-to-date.
Open your "App Store" application and verify that there's no available updates for the "Microsoft Remote Desktop" app
4) Try the other RDS connection method
There are two ways to connect to RDS; in a browser or using a remote desktop connection. If one method isn't working for you, try the other to see if the problem persists. Both methods are documented on this page under "Connecting and configuring RDS": https://answers.syr.edu/x/GYpDBg