Is it in a folder with the other two files? Did the kit viewer work for you? I'll try and find out whats wrong.
Some notes on actually replacing pre-made kits:
1. Download the kit and extract the 5 .vmp files. They will be labeled 512kit01.bmp, 256kit01.bmp or simular
2. Open the Kit Replacer, select the Kit you wish to replace and click import
3. From the window select the new kit you wish to import. e.g. 512kit01.bmp
4. Click Save to Gob
Important
5. You will need to do this for all 5 kit resolutions: 512, 256, 128, 64, 32.
6. Enjoy the new kit ingame