Unable to login using cPanel credentials

The plugin sometimes needs cPanel credentials at Step 1 (when it can't use cPanel's command-line API and falls back to the web API). Verify you have cPanel by visiting yourdomain.com:2083 or cpanel.yourdomain.com. Common causes of "Invalid username or password": using hosting-account credentials instead of cPanel-specific ones, stale credentials, or credentials for a different account. Contact your hosting provider to reset if needed.