It's important to note that if your SumUp card reader/s stop working after approx £500 is taken this is because you have not completed all the verification they require for using this type of financial service;
The Verification Checklist if your SumUp card reader stops working
In the SumUp online portal you may need to complete;
Identity: Upload a clear, color photo of your ID (Passport/License) and complete the "Liveness" selfie in the app. No scans or photocopies.
Business: Provide a website link, social media page, or a photo of a business invoice to prove what you sell.
Bank: Upload a bank statement (last 6 months). The name on the account must match your SumUp profile name exactly.
Other Reasons Payments Stop
Security Lock (System Sentinel): SumUp readers have internal anti-tamper sensors. If the reader is dropped, hit hard, or opened, it will permanently disable itself to protect card data. It will usually display "Device Blocked" or a similar error.
Battery Level: If the reader’s battery drops below 10%, it may refuse to initiate a Bluetooth connection or process a chip-and-pin transaction to prevent the device from dying mid-payment.
Incompatible Business: Even if you provide proof, SumUp does not support certain industries (e.g., adult services, gambling, tobacco, or some high-risk consulting). If your business falls into their "Restricted" list, they will close the account.
Self-Payment: Attempting to process a payment using your own personal credit or debit card on your own reader is a violation of their Terms of Service and will trigger an immediate account freeze.
Firmware Updates: Occasionally, a mandatory security update is released. If your SumUp App or Reader isn't updated to the latest version, payments will fail until the update is installed.
Quick Fix Tip
If the screen is frozen or won't connect, try a Hard Reset: Hold down the power button on the reader for about 10–15 seconds until it restarts. This clears the temporary cache without deleting your settings.
If the above does not solve the issue then you will need to reach out to SumUp.