In most of these cases it is a Windows rights problem, make sure that the necessary files have all access rights.
(Antivir; WindowsDefender and the like may interfere with this if the -.exe files in the Enderal folder are blocked,
see also mentioned Steam Discussion)
Another possibility are errors in the configuration files
please delete the 2 -.ini files under ...\Documents\my games\Enderal (Enderal.ini and EnderalPrefs.ini)
You can also temporarily disable one or more of the optimizations, these are ENBoost; OneTweak or OSAllocators.
(in the Launcher under Settings/Optimizations)
then try again.