In the case of an inaccessible SSD or deleted files, the first thing to do is to refrain from using the SSD to prevent data overwriting. You can try trusted recovery software tools that support SSD data recovery and scan for lost files. If the SSD is physically damaged or not recognised by the BIOS, you might need to seek professional help. Data can also get lost due to firmware issues or power outages. Regularly back up valuable files in the cloud or to a hard drive to avoid data loss in future.