Ps4 doesn't read discs anymore?

First thing to try is cleaning the laser lens using a lint-free swab moistened with isopropyl alcohol mixed with distilled water. 

You can buy cleaning kits for optical drives which have the correct materials.

The optical drive lens can quickly get dirty in any home where the console is close to the kitchen or where anyone smokes in the home (or burns scented candles or incense sticks).

If that fails then the laser head assembly needs changing. They can and do just fail, two years usage is certainly very early but it can happen anytime after the day the unit leaves the factory.

Have a look on YouTube. There are plenty of tutorials and the parts are VERY cheap, especially if you order directly from Chinese suppliers (but you have to wait what is typically between ten days and a few weeks for delivery). Or if you don’t feel confident then ask for prices for a professional repair. You can ask local repair shops but also check with Sony directly as they offer a fixed price repair service with warranty on all repairs. Sometimes they don’t charge for the job if they discover the fault was caused by poor materials or manufacturing errors.