Pattern to record: The partition exists but its file system is reported as unknown.

Identify the storage layer

APFS separates the physical device, container and individual volumes. Record which layer fails to appear or mount, and protect required files before changing container metadata or removing snapshots. One possible explanation is that the primary structure describing the volume cannot be read correctly.

Protect data before repair

A reinstall or erase is not a data-recovery first step. Formatting writes new headers over evidence needed for recovery.

Evidence to check on the protected copy

1. Protect the physical drive and inspect container, volume and snapshot structure before repair.
2. Inspect primary and backup headers without creating a new file system.

Recovery and verification

If the checks support this cause, restore a valid backup header or recover data using the correct geometry. Verification should cover mounting, startup, snapshots, file access, sleep and verified backup.

For an assessment of your Mac computer, contact AEPC in Burswood or call 027 908 8880. Provide the model and the conditions that reproduce this problem. Workshop visits are by appointment.