Sparkle works best with files stored locally on your Mac. If it's not recognizing your external or network drive, here's what to check:
First, grant full disk access: Go to System Settings → Privacy & Security → Full Disk Access and make sure Sparkle is turned on.
For external drives: Make sure the drive shows up in Finder before opening Sparkle.
For network drives: These can be tricky due to permission limitations. A good workaround is to organize files locally first, then move them to your network drive.