This error indicates that the *.pad files have not been created successfully or Allegro cannot locate the *.pad files at any location in its pad path. Follow these steps to troubleshoot this issue:
Verify the *.pad files have been created successfully during the import process
Each *_pad.scr in the downloaded *.zip file will create a *.pad file after successful execution
If the *.pad files were not generated by the allegro-builder.bat file, follow the instructions above under "What if the batch file won't run on my machine?" to manually create the *.pad files
Verify that Allegro can find the *.pad files in its padpath
Follow the instructions above under "How do I edit the padstack path?" to point Allegro to the where the *.pad files are stored.