If you receive a notification that the storage in this Mac needs service, it means an error with the Solid State Drive (SSD) has been detected.
The SSD in the Mac includes Self-Monitoring, Analysis and Reporting Technology (S. M A R.T.) hardware. This technology detects blocks of flash memory that have stopped working correctly. The problem can’t be fixed using Disk Utility or any other third-party app.
Back up as much of the data on the SSD as possible using Time Machine.
Contact Apple or an Apple Authorised Service Provider for service. Repairs performed by untrained individuals or using non-genuine Apple parts may affect the safety and functionality of the device.