If you have DX11 supporting card link to KB, installed the latest available client from Steam, but still encounter an issue on LiF:YO client launch please double check that all versions (2008, 2010, 2013) of 32-bit (they have _x86 at the end) C++ redistributables are installed. Please click on each of them and choose repair or install option
Redistributables can be found at \Steam\steamapps\common\Life is Feudal Your Own\_CommonRedist\vcredist
There should be something like this in your "Programs and Features" tool if you filter it by "C++"
Keep in mind that LiF:YO 126.96.36.199+ requires C++ 2015 redistributable which is now controlled by Steam and also available for installation from _CommonRedist\vcredist folder. If you are dedicated server owner which is hosted on 3rd party platform consider updating system with C++ 2015 manually as most likely you do not have Steam client installed on server side :)
Another noticeable change is that Microsoft includes Win7 SP1 and Win8 Update1 as mandatory requirement. Complete article can be found here https://support.microsoft.com/en-us/kb/2999226
Win8 users can find helpful information here or may try newer Win10 http://windows.microsoft.com/en-us/windows-8/install-latest-update-windows-8-1