I noticed some people are still going through this problem:
-- Fixes --
1. il2cppdumper files, metadata, and .so file are all in same folder
2. Use il2cppdumper latest version
Latest version here
3. Correct unity version
How to get unity version
4. Try different mode
5. Game has protection against dump, you can't hack
7. Run il2cppdumper as admin
8. [if above doesn't work] Use GUI Tool
Download GUI Tool
**Reply if you don't understand/need help**
-- Fixes --
1. il2cppdumper files, metadata, and .so file are all in same folder
2. Use il2cppdumper latest version
Latest version here
3. Correct unity version
How to get unity version
4. Try different mode
5. Game has protection against dump, you can't hack
7. Run il2cppdumper as admin
8. [if above doesn't work] Use GUI Tool
Download GUI Tool
**Reply if you don't understand/need help**