The PDF cannot be read
Remove passwords first using a tool you are authorized to use. For damaged files, save again from the original app or download a fresh copy. Renaming a file to .pdf does not change its format.
Page range errors
Use page numbers that exist in the document. Zero, numbers beyond the final page and reversed ranges such as “5-2” are invalid. Example: “1-3, 5”.
Slow or interrupted conversion
Try 150dpi instead of 300dpi or split the page range. On mobile, reduce other open apps/tabs and keep this tab active. Avoid submitting the same job repeatedly while queued. If cancellation cannot be confirmed, a server job may continue.
A download link disappeared
Browser links do not survive a refresh, a new file or moving to the next batch. Server results expire after the stated time. Save results promptly and convert again from your original if needed.