Mirador - viewer

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

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "/api/digital_items/82657/2/manifest.json/",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-9828fde7-48a5-45ea-9506-7a10c80a9b6d",
      "cw-708c45e9-7c41-4f43-9267-a64efe8bea75"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a72f1206-439b-4a1f-9971-8c25fec7cffb",
    "manifestId": "/api/digital_items/82657/2/manifest.json/",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "annotations",
    "thumbnailNavigationId": "cw-708c45e9-7c41-4f43-9267-a64efe8bea75",
    "thumbnailNavigationPosition": "off",
    "loadedManifest": "/api/digital_items/82657/2/manifest.json/",
    "canvasIndex": 0
  }
}