App Store Connect API key authentication failed with 401 error in fastlane

TL;DR

Rebuild the API key configuration with the correct key id, issuer id and the original .p8 file, and confirm the key has not been revoked. The .p8 can be downloaded only once, so if it is lost or the CI copy is truncated, create a new key in App Store Connect, store the file in CI secrets as a file or base64 exactly as issued, and update the fastlane lane. Also check the runner clock, because expired or skewed timestamps produce 401s.

App Store Connect API key authentication failed with 401 error in fastlane

Use this when

• fastlane lanes using the App Store Connect API return 401 or Not Authenticated.
• The key was moved between CI systems or re-uploaded as text.
• A team member revoked old keys during a cleanup.

Not for this skill when

• The key works but a specific call returns 403. That is a permissions or role issue, not authentication.
• You authenticate with an Apple ID session instead of an API key. The session expiry flow is different.

Steps

1. In App Store Connect, Users and Access, Integrations, confirm the key id exists, is active, and note its role and issuer id. Verify: the key is confirmed active, or confirmed revoked so a new one is created
2. Verify the .p8 file in CI is byte-identical to the downloaded original: it should begin with the private key header line and be 10 lines or so, untruncated. Verify: the stored file matches the expected format with no missing lines or added quoting
3. Pass the key id, issuer id and key content to the fastlane api key action from CI secrets, avoiding hand-copied values with stray spaces. Verify: the lane logs the key id it used, matching the portal value
4. Check the CI runner date and time are synchronised, since the API signs short-lived tokens from the system clock. Verify: the runner time matches a reference time source within a minute
5. Run a harmless read-only call through the lane, such as fetching the app list, before retrying the upload. Verify: the read call returns 200 with app data
6. If the original .p8 is lost, create a replacement key, update CI, and revoke the lost key in the portal. Verify: the new key authenticates and the old key shows revoked
7. Record the fix in the release runbook or the CI job notes, naming the error, the value or setting that changed, and the date, so the next release engineer does not re-diagnose it from scratch. Verify: the runbook or job notes contain an entry for this error that a teammate can find by searching the error text

Why it happens

The API authenticates with a signed JWT built from the key id, issuer id and the .p8 private key. A 401 means the token could not be verified: wrong pairing of id and file, a truncated or re-wrapped key file from a secrets UI, a revoked key, or a clock far enough off that the token is born expired. The API returns no finer detail, so each input must be verified independently.

In practice this failure is rarely a one-off. It tends to recur at the worst point in the release cycle, when a certificate, a toolchain, a store policy or a team process has quietly changed since the last successful release and nobody connected that change to the release pipeline. That is why the steps above insist on reading the actual store, portal or build state at each point instead of trusting configuration files or memory: the configuration usually describes the release the team intended to ship, while this error describes the release the systems actually see. Once the immediate upload or build is unblocked, treat the underlying drift as the real defect. Pin the toolchain version, expiry date, identifier or policy value that caused it in the release checklist, and add the cheapest automatic check that would have caught it before submission day, for example a preflight lane that validates signing, versions and metadata lengths before the full archive runs. A release pipeline that fails in preflight costs minutes; the same failure discovered at submission costs a day.

Variants and edge cases

fastlane 401 Not Authenticated App Store Connect API

The exact API wording variant; verify id, issuer and p8 as a set. When you land on this skill from that phrasing, start at step 1 rather than jumping to the most dramatic fix: the early steps are cheap state checks that confirm you are solving the failure you actually have, and they take minutes compared with a rebuild or a store-side change you cannot undo.

appstoreconnectapikey 401 CI fix

CI phrasing; the stored key file is the prime suspect. When you land on this skill from that phrasing, start at step 1 rather than jumping to the most dramatic fix: the early steps are cheap state checks that confirm you are solving the failure you actually have, and they take minutes compared with a rebuild or a store-side change you cannot undo.

Edge case: base64 double encoding

Keys stored base64-encoded twice decode to base64 text, not a key. Decode once and check for the header line. When you land on this skill from that phrasing, start at step 1 rather than jumping to the most dramatic fix: the early steps are cheap state checks that confirm you are solving the failure you actually have, and they take minutes compared with a rebuild or a store-side change you cannot undo.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_zJxOyqhZWQxLJYUVQmZdjg