How do I fix the NotebookLM "error uploading source" message?

"Error uploading source" in NotebookLM means the content could not be accessed or extracted. Common causes:

• The URL requires login or is behind a paywall
• The page blocks automated crawlers
• The file format is not supported
• A temporary server issue on Google's side

To fix it: open the URL in an incognito window to confirm it is publicly accessible. If it loads there but fails in NotebookLM, the site is likely blocking crawlers — copy the text manually and paste it as a text source. For file errors, convert to PDF or plain text. If it looks like a server issue, wait a few minutes and try again.