PLEASE make some searches in this forum before posting. When posting a download issue, state the browser (Firefox, Chrome, ...) version, VDH and coapp versions you are running, your operating system (Windows, Mac, Linux) and share a link to a page containing a video you have problem with.

A few links that may be of interest:

Frequently Asked Questions: https://www.downloadhelper.net/faq

Latest version of the add-on for Firefox: https://addons.mozilla.org/firefox/addon/video-downloadhelper/

Latest version of the add-on for Chrome: https://chrome.google.com/webstore/detail/video-downloadhelper/lmjnegcaeklhafolokijcfjliaokphfk

All versions for Firefox: https://addons.mozilla.org/en-US/firefox/addon/video-downloadhelper/versions/

Latest Companion App: https://www.downloadhelper.net/install-coapp

All versions of CoApp: https://github.com/mi-g/vdhcoapp/releases/

Beta versions for Firefox: https://www.downloadhelper.net/firefox/betas

Video DownloadHelper Q&A