> ## Documentation Index
> Fetch the complete documentation index at: https://docs.heydollr.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Knowledge Base

> Troubleshooting guides for common Dollr API errors and integration issues.

Step-by-step fixes for errors you may hit during integration. For HTTP retry rules and idempotency, see [Error handling](/guides/error-handling). For a full table view, see [Error catalog](/reference/error-catalog).

## Authentication

<CardGroup cols={2}>
  <Card title="401 — Invalid credentials" icon="key" href="/knowledge-base/invalid-credentials-401">
    Expired or missing Bearer token.
  </Card>

  <Card title="403 — Forbidden" icon="lock" href="/knowledge-base/forbidden-403-unverified">
    Verification or feature gates.
  </Card>
</CardGroup>

## Validation & state

<CardGroup cols={2}>
  <Card title="422 — Validation errors" icon="file-lines" href="/knowledge-base/validation-422">
    Payload and field fixes.
  </Card>

  <Card title="Duplicate reference_id" icon="copy" href="/knowledge-base/duplicate-reference-id">
    Idempotency conflicts.
  </Card>

  <Card title="Session expired" icon="clock" href="/knowledge-base/session-expired-or-invalid">
    Stale or wrong session\_id.
  </Card>
</CardGroup>

## Payments & operations

<CardGroup cols={2}>
  <Card title="Stuck in PROCESSING" icon="hourglass" href="/knowledge-base/payment-processing-status">
    Normal MoMo delays vs real failures.
  </Card>

  <Card title="Card 3DS failed" icon="credit-card" href="/knowledge-base/card-3ds-failed">
    requires\_action and client\_secret.
  </Card>

  <Card title="Payout passcode" icon="lock" href="/knowledge-base/payout-passcode-error">
    Passcode setup and payload errors.
  </Card>

  <Card title="Wallet balance" icon="wallet" href="/knowledge-base/insufficient-wallet-balance">
    Payout failed — low wallet balance.
  </Card>

  <Card title="429 — Rate limit" icon="gauge" href="/knowledge-base/rate-limit-429">
    Backoff and Retry-After.
  </Card>

  <Card title="5xx — Server errors" icon="server" href="/knowledge-base/server-error-5xx">
    When to retry and escalate.
  </Card>
</CardGroup>