Hi Kamryn,
On your network are you using ZScaler or some other kind of proxy? I had this problem before with all Mendix projects that used Studio Pro 10.3+. At the end I found out it was because I needed to add the Root Certificate (of ZScaler in my case) into the installed JDK's keystore that Studio Pro uses.
You can find more information about it here on this other question I have answered where they have the same problem as you:
https://community.mendix.com/link/space/community/questions/134236
I hope that helps you solve your problem, best regards!