I am a craft potter selling mainly from specialist, often outdoor, markets with uncertain internet access. My SumUp Solo card reader, used successfully at fewer than 10 markets and now out of warranty, is suddenly giving me a screen message “SumUp blocked”. The website and the chatbot say this is permanent and caused by being dropped, exposed to low temperatures or not keeping it charged. In my case the first two don’t apply and nothing in the instructions indicate the latter is necessary. Similarly affected users I found online complain it is hard to speak to a human at the company and suggest it is disabling out-of-warranty card readers to make people buy another. I want the company to replace my little-used reader – after all they have taken a percentage of my sales – and as a small trader I can’t afford the £80 to replace it and risk the same thing happening. JC, Carnforth The advent of mobile card readers has been brilliant news for small businesses, clubs and charities so I was sorry to hear of this problem and wondered if it was a wider issue. When I contacted SumUp it could not comment on individual cases, but says it takes feedback from merchants seriously. It says: “SumUp does not disable devices after warranties expire. As a financial company committed to ensuring the security of consumers and our merchants, our devices are designed to lock in the event of several factors, such as suspected tampering, extreme temperature change, or forcible impacts. “In the rare instances when a merchant finds their device locked or otherwise defective, merchants may be eligible for a free replacement and are encouraged to reach out directly to our customer support.” It has been in touch with a new reader and you are pleased.