Make sure the name is correct. Folder name, DEF File and typed name in select.def file be the same.
Remember it! Uppercase, lowercase or special characters must match.
Is the path correct? To add a stage, you need to type “stages/”, the folder name that contain stage files, another / and the .DEF file name with the “def” extension, without spaces.
Some stages don’t have a folder that contains them. In that case, the path is “stages/” and the .DEF file name.
Did you extract all files from the compressed file? Is your file corrupt?
Make sure you extracted the character folder completely.
Or check the integrity of your file.
Open your file using Winrar, click on "Test" button. It will test your file and show you an alert message box.
If your file show errors, download it again. If it doesn't, the file was uploaded incomplete.
Can the stage run on your Mugen version?
Mugen has 3 different version: Pre 1.0, 1.0 and 1.1 and some stages may not run with one of them.
In that case you need to test with another Mugen version.
Stages with zoom effect only run on Mugen 1.1