The name you put in the select file have to be the same name that is on the character .def file unless the character folder have the same name.
If the folder name is Demitri and the .def file inside the folder is Demitri too you can just put Demitri in the select.

If the folder is diferent from the .def file like -> the folder is cvsdemitri and the .def is Demitri, you have to put this on the select:

cvsdemitri\Demitri.def
the first one being the folder name \ then the .def name always with .def after the name.

• Make sure you're editing the right .def file. Sometimes screenpacks comes with multiple select.def files for specific resolutions or number of slots. See what file is being used by your system.def.
• Make sure the spelling is correct. If the .def of the character and the folder have the same name (eg: folder name is Demitri and the file is Demitri.def), you can put only "Demitri" in the select.def, otherwise you must type the whole directory: "Demitri/Demitri_ex.def".
• Try it in a clean install of mugen.

Maybe its bc you're spelling it as "Dimitri" and not "Demitri"....

the folder of the char its "demitris"