Solution: Reset your settings. Delete the RadiantViewer.ini file located in %APPDATA%\RIA (Windows) or ~/Library/Preferences/ (macOS). Restart Radiant – it will default back to Viewer mode with no activation prompt.
Go to microdicom.com. Navigate to "Products" > "Radiant DICOM Viewer" > "Buy License." You will purchase a license key sent via email. This is a perpetual license for a specific version (e.g., v.3.x). radiant dicom activation code
If you decide to stay with the free, legal version (which is what 80% of users do), follow this setup: Solution: Reset your settings
That’s it. You have a professional-grade DICOM viewer, legally, for free. That’s it
Your Radiant DICOM will now show “Pro” in the title bar, and all network features become available.
If you need the Pro features, here is the lawful and safe path.
You might see a dialog box that says:
“This feature requires a valid Radiant DICOM Activation Code. Please enter your code or purchase one.”