Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - Technical Issues ERROR: Failed to create rendering device!

A clean re-install of graphics drivers may help.

There are also programs that may lock the DDI to a lower version. For example one person online had a problem with a USB adapter / receiver designed to let them connect their monitor wirelessly. An Asus overclocking tool can also be at fault (Directx 11 and DDI 9Ex error - solution for ASUS cards).