The "final download link" is the last URL in that chain. The error message states that this final URL pointed to something that is not a downloadable file. Instead, it pointed to:
: Some sites force low quality if they detect too many concurrent downloads. Go to Settings > Plugins > [Site Name] and enable "Try to recognize limit" to help JDownloader identify and wait out these blocks Fixing Broken Installations The "final download link" is the last URL in that chain
: If a private link fails, try creating a "Public Share Link" for the file in your browser and adding that to JD instead. 5. Specialized Troubleshooting for Streaming The "final download link" is the last URL in that chain