A. 1. Check Credentials: Ensure that you are entering the correct username and password. If you have forgotten your password, use the 'Forgot Password' option to reset it. 2. Network Connection: Make sure you have a stable internet connection. Try switching between Wi-Fi and mobile data to see if that resolves the issue. 3. App Permissions: Go to Settings > DingTalk and ensure that all necessary permissions are granted, especially for network access.

B. 4. Clear App Data: If you are still facing issues, go to Settings > General > iPhone Storage > DingTalk, and select 'Offload App'. This will clear temporary data without deleting your account information. Reopen the app and try logging in again.