The laser lens gets dusty, or the Blu-ray diode weakens over time. Use a slim lens cleaning disc (for slot-loaders). If that fails, the Blu-ray laser may be dead – the drive is then only useful for DVDs/CDs.
Manufactured by (now Panasonic), the UJ240AS is a slim, slot-loading Blu-ray reader and DVD/CD writer. It was commonly found in high-end laptops from Toshiba, Sony, Dell, and HP around 2010–2014. matshita bd-mlt uj240as