MacBook Pro doesn't recognize internal SSD
It may be that your hard drive is no longer working properly and needs to be replaced.  However, you can try to diagnose using the Apple Diagnostics.

If hardware problems are indicated or Apple Diagnostics does not recognize your hard drive either, it may be worth looking for a Retail Store or AASP to get it looked at.

If you are still in Apple's hardware coverage, such repair will usually be free of charge.