Apple Mail "send" button is greyed out on replies until I tap to or cc field
Following up on this thread👇🏽. Wondering if there is an obvious fix for this issue.
Send button greyed out in Apple Mail.... - Apple Community
MacBook Air
If all else fails, and since mail is an integral part of the OS, consider reinstalling the OS via the Recovery Panel: How to reinstall macOS - Apple Support
"Reinstall macOS"