Linking doesn’t seem working

Hello, I bought the plugin and love it - nice work! I have a problem with linking: - I set it to auto-link posts, but no link shows up, and the manual run gives a red cross. No error in the logs - I set it to manual and added about 15 post links, but no link shows up, and the manual run gives a red cross. No error in the logs Do you know what I am doing wrong? Thank you