Hello, there was an update with a bug fix.
Ummy Video Downloader OS Windows 1.10.4.​​​0
Ummy Video Downloader OS MAC 1.69
Please update or reinstall from our website: https://videodownloader.ummy.net

Hello, please, send us more details regarding the problem.

Hello, in order to help you better I need the following information.
Please, send me the information listed here: http://en.savefrom.net/user.php?info=1

Could you please send a few links you can't download. We will check it out.

Hello, what exactly did you download? Describe in more detail.

Hello, this extension has been fixed. Please, update or reinstall it from our site.
The latest version is 8.29: http://en.savefrom.net/user.php#helper_install
Thank you for using Savefrom.Net browser extension

Hello, we’d like to help you, but we will need some info about your browser and the installed extension first.
Please, go here http://en.savefrom.net/user.php?info=1
Copy the details that you see and send them back to us.
Please also send us some video links that you can’t download.
Thank you for contacting Savefrom.Net support !

Hello, in order to help you better I need the following information.
Please, send me the information listed here: http://en.savefrom.net/user.php?info=1

Hello, in order to help you better I need the following information.
Please, send me the information listed here: http://en.savefrom.net/user.php?info=1

Hello, we’d like to help you, but we will need some info about your browser and the installed extension first.
Please, go here http://en.savefrom.net/user.php?info=1
Copy the details that you see and send them back to us.
Please also send us some video links that you can’t download.
Thank you for contacting Savefrom.Net support !

Hello, in order to help you better I need the following information.
Please, send me the information listed here: http://en.savefrom.net/user.php?info=1

For the better understanding it'll be great to see a screenshot with the error.