SYMPTOM
AuthenticationFailed: signature did not match (Storage Shared Key)
CAUSE
The Shared Key signature is wrong: rotated/wrong key, wrong key slot (key1 vs key2), VM clock skew beyond ~15 minutes, or Azurite dev-key vs real-key mixup. With SDKs it is never the string-to-sign.
CONFIRM IT
CONFIRM: every request fails identically (clock skew or wrong key); only some fail (key rotated mid-run). `az storage account keys list` and compare which slot the connection string uses. Check VM clock against NTP.
FIX
FIX: regenerate the connection string from the current key; resync the clock (w32tm /resync or NTP); point Azurite configs at the well-known dev key and real accounts at real keys. Long term: move to identity auth and delete the key dependency.
VERIFY
VERIFY: a simple `az storage blob list --auth-mode key` (or SDK list) succeeds; then the app's calls succeed.