If you upgraded your Ubuntu to 17.10, you may encounter black screen issue by Worksnaps Client or Linux's Scrot command. Because Ubuntu 17.10 use Wayland as default display server, Wayland is new generation display server and will replace old X11. There is a common issue in Wayland(Captures black screen only on Wayland). For Workaround solution, please select "Ubuntu on Xorg" to login.

Here are the steps:

1. Log out the current user.

2. Select "Ubuntu on Xorg" in Login dialog.

3. Start Worksnaps Client as usual.