Mirador - viewer

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

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "/api/digital_items/82588/2/manifest.json/",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-b6b1f708-85b9-4384-ac58-80ca27552c1f",
      "cw-e82b7ae6-3dcb-4d32-9458-e980c826ec6e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-29046ea0-05e4-4596-9165-9fe9104819c2",
    "manifestId": "/api/digital_items/82588/2/manifest.json/",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "annotations",
    "thumbnailNavigationId": "cw-e82b7ae6-3dcb-4d32-9458-e980c826ec6e",
    "thumbnailNavigationPosition": "off",
    "loadedManifest": "/api/digital_items/82588/2/manifest.json/",
    "canvasIndex": 0
  }
}