After some research, John discovered that his game console didn't have the English language pack installed for Call of Duty Modern Warfare 3. He realized that he needed to download the language pack to fix the issue.
If you're having trouble finding the download button, let me know: What are you on (PS5, Xbox, PC)? What region was your game purchased in? Are you getting a specific error code ? English Language Pack For Call Of Duty Modern Warfare 3