Scheduler can download any file if it does not require interaction with user. If WeTransfer requires to click some button, or enter a code, or wait while "download prepares" - it will likely not work with RadioBOSS. In roder to download such things, RadioBOSS will have to emulate user actions, but that's likely to be against WeTransfer service terms of servide (ToS), and therefore not acceptable.
If it provides a direct download link, then it can be used in RadioBOSS. So I suggest you to try downloading a file, or somehow finding a direct link (if they have paid service, it also usually includes direct download links).