The HTTP header ACCEPT is missing or its value is invalid
This message shows up in 2 different situations. Pick the one that matches yours:
- File upload via /Files/add: nometadata works under OData v4 — an empty OData-Version breaks SPFx when you leave out Content-Typenometadata + octet-stream under the default OData v4; an empty OData-Version without Content-Type throws inside SPHttpClient; plus the empty-filename mobile camera trapCause and fix →
- Drop __metadata from write bodies — odata=verbose needs OData v3, and SPHttpClient sends v4Old-tutorial payloads 400 as plain JSON, and switching to odata=verbose 400s again under SPHttpClient, which sends odata-version: 4.0; write plain JSON without the type hint, or blank odata-version where the verbose form is really neededCause and fix →