As a seasoned Full Stack developer named Ganesh, I've been vigorously working with OpenCart for years and have intimate expertise in troubleshooting. Delving into your specific problem with the extension page returning an 'ERROR' message, I have theories that could help resolve the issue.
First off, without any recent changes to your system or server, it's likely that the problem lies within the OpenCart platform itself. This entails looking into how the application handles extensions and potential conflicts that could arise out of nowhere. Having worked with vast array of technologies like Reactjs, NodeJs, Next Js, Bootstrap and JavaScript , I have experience in not only identifying such conflicts but also fixing them efficaciously.
My proficiency in Laravel further equips me to tackle your concern efficiently. Laravel and Opencart share core design principles, making fixing Opencart glitches second nature to me. With me on board, you're gaining not just an expert in OpenCart but a wider range of web developing skills that will prove valuable beyond this immediate troubleshooting scenario. Let's connect so I can dive deep into unraveling this error puzzle for you!