Maybe you have recently changed your GitHub username, the old profile link will break and return 404. Verify the exact URL, GitHub URLs are case-insensitive, but sometimes copy-pasting causes errors.

Sometimes GitHub flags accounts for unusual activity (spam detection, violation, or security concerns). In that case, your account looks normal when you’re logged in, but it’s hidden publicly (404 for others). Check your email for any notices from GitHub. If you see “suspension” or “flagged” messages, you’ll need to contact GitHub Support.