Pattern to record: Files are visible but one computer or application cannot open or write them.

Identify the storage layer

Confirm that the external volume is actually exFAT and record which computer or device last wrote to it. Compare the cable and enclosure as well as the volume; a shared drive may encounter different host policies on Windows and macOS. exFAT does not store NTFS-style owner and ACL records; access failure can arise from host policy, a read-only mount, application restrictions or damaged data.

Protect data before repair

Cancel format prompts until required files are secured. A blanket permission-reset command cannot add features that the file system does not support.

Evidence to check on the protected copy

1. Test the device and connection read-only before deciding whether the issue is media or file-system damage.
2. Record the exact error, check mount state and device write protection, then compare authorised access on another compatible host without modifying the only copy.

Recovery and verification

If the checks support this cause, correct the verified host or application restriction, or recover damaged files; do not invent ownership records for exFAT. Verification should cover cross-platform mounting, large file transfer, safe removal and backup.

Reference: Microsoft technical guidance.

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