To address the issue of your Upside app going blank and displaying a cash rewards balance of zero, follow these steps:

1. Reboot Your Device
Start by turning off your smartphone and then turning it back on. This can clear temporary glitches that may be affecting the app's functionality.

2. Check for App Updates
Ensure that the Upside app is up-to-date. Open the app store on your device and see if there are any available updates for the Upside app. If there are, install them.

3. Clear Cache (if applicable)
For Android users, go to Settings > Apps > Upside > Storage and select "Clear Cache." This may help if temporary files are causing the app to malfunction.

4. Reinstall the App
If the above steps do not resolve the issue, uninstall and then reinstall the Upside app:
- Uninstall the app from your device.
- Go to your app store and download the Upside app again.
- Log in with your existing credentials. Reports indicate that many users find their cash rewards and account history restored after this action - learn more - learn more.

5. Log In Again
After reinstalling, log back into your account. If your account appears empty, try re-adding the payment method you initially used to see if that restores your previous balance - learn more.

6. Contact Customer Support
If your rewards and account history are still missing, it's time to reach out to Upside customer support. They can assist in recovering your account information. You can usually find support contact information within the app or on the Upside website - learn more.

Make sure to follow these steps thoroughly to resolve the issue with your Upside app and restore your cash rewards.