--- cuppy_hub: azure cuppy_path: reference/functions/errors.md cuppy_section: docs cuppy_doc: FFDY-C9BC cuppy_doc_uuid: e65d7022-be66-44d1-8b3f-435b9e61ea57 cuppy_permalink: https://cuppy.io/azure/d/FFDY-C9BC cuppy_version: 1 cuppy_updated: 2026-10-23T16:16:52.575Z cuppy_canonical: https://cuppy.io/azure/docs/reference/functions/errors cuppy_mcp: https://cuppy.io/mcp cuppy_body_sha256: 03b47fa945ef0b336050d19695f42dcac24c150ab0fd9916393f5a66bb1198fa # cuppy_body_sha256 is over the document body ALONE, excluding both generated blocks. --- # Azure Functions errors **A function app is a host that needs its own storage account (`AzureWebJobsStorage`) before it runs any code.** Most "won't start" errors are that connection: missing, wrong, unreachable, or authenticated in a way the account refuses. Read the app's **Diagnose and solve problems** blade and Application Insights `traces` first; AZFD events land there even when the host can't start. ## Host won't start | Message / code | Cause → fix | Check | |---|---|---| | Portal: `Error: Azure Functions Runtime is unreachable. Click here for details on storage configuration.` | The host can't reach its storage account: deleted, settings removed (often by a slot swap or an ARM script that replaced all settings), keys rotated under a connection string, firewall without a network path, or Shared Key turned off while the app still uses a connection string. Fix the cause below, then restart | `az functionapp config appsettings list -n -g --query "[].name" -o tsv` (names only; never print values) | | `AZFD0001` `AzureWebJobsStorage app setting is not present.` | Setting missing. Set either a connection string or the identity form (`AzureWebJobsStorage__accountName` + `__credential` + `__clientId`) | Same | | `AZFD0002` `Value of AzureWebJobsStorage app setting is invalid.` | Not a valid connection string. Also raised for a **Key Vault reference** in that setting, where Microsoft says to suppress it | The value's shape (don't print it) | | 403 from storage in host logs, identity form | The identity lacks **Storage Blob Data Owner** on the account (the minimum for the host). Add **Storage Table Data Contributor** too, or the host can't write diagnostic events. Blob triggers also need Storage Queue Data Contributor and Storage Account Contributor (`reference/functions/hosting-and-host-storage.md`) | `az role assignment list --assignee --scope -o table` | | `KeyBasedAuthenticationNotPermitted` in host logs | Shared Key is off and the app uses a connection string (the CLI writes one, see below). Switch to the identity form. Consumption and Elastic Premium still need a connection string for the Azure Files content share (`WEBSITE_CONTENTAZUREFILECONNECTIONSTRING`) | `reference/storage/sas-and-key-errors.md` | | Storage `AuthorizationFailure` / host timeouts with the account firewall on | No network path: VNet integration plus a VNet rule or private endpoints for `blob`, `queue`, `table` (and `file` on plans with a content share) | `reference/storage/network-and-firewall.md` | | `AZFD0004` Host ID collision (error in v4: the host stops) | Two apps or slots share a storage account and the first 32 characters of their names. Use separate accounts, shorter names, or explicit host IDs | App names sharing a storage account | | `AZFD0005` External startup exception | A .NET startup class threw during initialization; the host retries and logs it repeatedly | The exception's stack trace | | `AZFD0011` `The FUNCTIONS_WORKER_RUNTIME setting is required` (warning); `AZFD0013` runtime mismatch | The setting is missing, or doesn't match the deployed payload. Flex Consumption doesn't use this setting: the runtime is `functionAppConfig.runtime` | `az functionapp config appsettings list …` | | `The Function App has reached daily usage quota and has been stopped until the next 24 hours time frame.` | A daily quota you set was hit. Raise or remove it, then restart | Function App settings in the portal | | Flex Consumption: gRPC `System.TimeoutException` at start | App initialization exceeded **30 seconds** (not configurable). Move slow work out of startup | Startup duration in traces | | Docker logs `manifest unknown` (container function apps) | The image or tag doesn't exist | `reference/container-registry/errors.md` | | App unreachable from the portal only | Inbound access restrictions or an internal App Service Environment block the portal's calls to the app and Kudu | Access restrictions on the app | ## Node.js (programming model v4) | Message | Cause → fix | Check | |---|---|---| | `No job functions found. Try making your job classes and methods public. …` / `No HTTP triggers found.` | The host loaded no registrations. Usually `package.json` `main` doesn't match the compiled files (TypeScript: `dist/src/functions/*.js`), the build didn't run before zipping, or an import threw at load. Set `FUNCTIONS_NODE_BLOCK_ON_ENTRY_POINT_ERROR=true` so entry-point errors surface. Needs runtime 4.25+, Core Tools 4.0.5382+ | Traces where `message has "entry point"` | | `Exception: undici_1.Request is not a constructor` | Node.js too old; use 22 or later | `functionAppConfig.runtime.version` or `az functionapp config show` | | `WARNING: Failed to detect the Azure Functions runtime. Switching "@azure/functions" package to test mode …` | An old `applicationinsights` dependency; use `^2.7.1` or later | `package.json` | | HTTP streaming does nothing | Needs `@azure/functions` 4.3.0+, runtime 4.28+, and `app.setup({ enableHttpStream: true })` | — | ## Azure CLI `az functionapp create` errors (2.91, from its source) | Message | Cause → fix | |---|---| | `Storage account '' has no '' endpoint. It must have table, queue, and blob endpoints all enabled` | Host storage must be a general-purpose account (`StorageV2`), not Blob-only or Files-only | | `Storage type is not allowed` | The CLI accepts `Standard_LRS`, `Standard_GRS`, `Standard_RAGRS`, `Standard_ZRS`, `Standard_GZRS`, `Premium_LRS` only (not `Standard_RAGZRS`) | | `The Consumption plan does not support storage accounts with network restrictions. …` | Use Flex Consumption, Premium or Dedicated | | `The storage account you selected "" has networking restrictions. No virtual networking was configured so your app will not start. …` | Pass `--vnet` and `--subnet`, or `--configure-networking-later` and add them before the app runs | | `usage error: --runtime RUNTIME required for linux functions apps without custom image.` | Pass `--runtime node --runtime-version 22` (or 24) | **The CLI always lists the storage account's keys and writes a connection string into `AzureWebJobsStorage`.** It needs `listKeys` on the account, and the app breaks once Shared Key is off. To create keyless, use Bicep (`guides/functions/deploy-typescript-function.md`) or switch the settings to the identity form right after create. --- You are reading one file. The same content is free over MCP at https://cuppy.io/mcp with no signup: ranked search across all 107 documents in this hub, the merged view when you work in a layer, known workarounds matched to the error you hit, and depth control so you spend tokens on what you need. Start with the `_hello` tool. 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