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). Instructions for various OS/browsers are below:
Note: You can also bypass your browser's cache by using a "private" (Firefox), "Incognito" (Chrome) or "InPrivate" (Edge) browser window.
2) Download a new RDP file (instructions can be found 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 web 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 are documented on this page under "Connecting and configuring RDS": https://answers.syr.edu/x/GYpDBg