For offline workstations (common in secure radiology environments), Paxera offers an offline activation file method. Contact support to generate a license.dat file.
It might be tempting to search for a free activation key online, but this carries significant risks: Trial license activation - RadiAnt DICOM Viewer radiant dicom viewer activation key
: For legacy or specific license types, double-click the .radiantlic file sent to your email or select "Supply license key file" during a custom installation. License and Pricing Overview Paid license activation - RadiAnt DICOM Viewer radiant dicom viewer activation key