"Failed to create Direct3D 9ex device"

[Reaper]

It started to apperars it today and I don't know how to fix it. Someone could help me please?

[Bread]

Just from reading Steam support and a video online, there's a couple things you can try to do.If one doesn't work, try the other.

-Lower your DirectX level through launch options.You can do this by Right-Clicking on Undertale, click properties, general, and set launch options.Enter "-dxlevel 81" without quotes

-Update your GPU(s) drivers.If you don't know what model your Graphics are, here's how to find it.Assuming you're using Windows, press the Windowskey+r or search for the desktop application Run and in the box that comes up, type in dxdiag, which is the DirectX diagnostic tool that shows the model of your graphics.Just go to the site of the GPU brand you're using and find that model's drivers.It's possible that your computer will automatically update the drivers depending on the computer.

-Keep your PC up-to-date, period.This includes regular updates and .net framework

[Reaper]

Didn't work.
But Worms is working, Undertale that's not working and I don't know what else I still can do to fix it.

[Bread]

Originally posted by BitterTaste:

Didn't work.
But Worms is working, Undertale that's not working and I don't know what else I still can do to fix it.

The last thing I suggest is to go back to Undertale's launch options, and enter "-w xxxx" and "-h xxxx" with the Xs being the resolution of your computer right now.Include the spaces but remove the quotations
For example, I would enter -w 1280 and -h 720

[Reaper]

Solved the problem, when I finally could update my video driver.
Thanks everybody.