## TL;DR

Square returns UNAUTHORIZED because the access token expired. Refresh the OAuth token and retry; if refresh fails, the merchant needs to re-authorize.

## Error

```text
UNAUTHORIZED on payments with an expired access token
```

## Steps

1. Try the refresh token to get a new access token Expected: you have a working token again.
2. Retry the payment with the new token Expected: it succeeds.
3. If refresh fails, send the merchant through OAuth re-authorization Expected: a fresh token pair is issued.
4. Add proactive refresh before expiry Expected: it does not lapse again.

## When to use

- UNAUTHORIZED on Square payments
- The access token expired

## When not to use

- Wrong credentials entirely (then refresh fails too)
- Token revoked by the merchant (then re-auth is the only fix)

## Tool compatibility

- Square OAuth token lifecycle
- Payment integrations

## Variant phrasings

### square unauthorized expired token

Refresh the access token and retry; re-auth if refresh fails.

### square payments 401

Same: token lifecycle, not your request shape.

## Why it happens

Access tokens are short-lived by design. Agents store the first token and never implement refresh until the first expiry pages them.

## Edge cases

- Square refresh tokens also expire; handle the full re-auth path
- Sandbox and production tokens are separate

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_HmXy72VXDlFq2ulgse4zbg