Mirador - viewer

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

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "/api/digital_items/132983/2/manifest.json/",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-45510abd-91b0-41ab-99b5-3edac61662f0",
      "cw-5fcb2a6d-ed69-4319-9537-943f8c0582c8"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-15f8b09e-26e2-4564-990f-db272073aa08",
    "manifestId": "/api/digital_items/132983/2/manifest.json/",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "annotations",
    "thumbnailNavigationId": "cw-5fcb2a6d-ed69-4319-9537-943f8c0582c8",
    "thumbnailNavigationPosition": "off",
    "loadedManifest": "/api/digital_items/132983/2/manifest.json/",
    "canvasIndex": 0
  }
}