Mirador - viewer

SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "/api/digital_items/127283/2/manifest.json/",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-68180be1-1ef2-4611-b583-6a96d93d4519",
      "cw-1bb4ef39-cefb-4bfb-bb67-3a9359b8e6d1"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-17aff355-a359-478b-a2e9-1996368a8d9d",
    "manifestId": "/api/digital_items/127283/2/manifest.json/",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "annotations",
    "thumbnailNavigationId": "cw-1bb4ef39-cefb-4bfb-bb67-3a9359b8e6d1",
    "thumbnailNavigationPosition": "off",
    "loadedManifest": "/api/digital_items/127283/2/manifest.json/",
    "canvasIndex": 0
  }
}