A. If the data usage tab is not functioning, try restarting the app. If the issue persists, clear the app's cache by going to 'Settings' > 'Apps' > 'TP-Link Tether' > 'Storage' > 'Clear Cache'. This may resolve temporary glitches.

B. If clearing the cache does not work, consider uninstalling and reinstalling the app to ensure you have the latest version.