An SSD missing from firmware is a different problem from a disk visible in firmware but missing in Windows. Check the first point of failure.
Protect your files first
Back up important files when possible. If the drive is encrypted, locate the BitLocker recovery key before recovery changes. Stop if storage appears to be failing or this is a work or school managed PC.
What to record
Firmware drive listing, cable or slot changes, OEM diagnostics, and backup status.
The exact message, Windows version, and whether the desktop still opens matter more than a guess based on the symptom name.
Try these safer checks
Use the PC or SSD maker’s official diagnostics and model-specific connection guidance.
Change one thing at a time. After each check, see whether the same symptom returns and write down what changed.
When to stop and get help
Do not initialize, format, or repartition a drive containing needed data.
If this is a work or school device, contact its administrator before changing managed settings.
Keep track of your checks
This checklist stays in this browser session. It is not sent to WinErrors.