Mirador - viewer

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

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "/api/digital_items/111616/2/manifest.json/",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-425e6412-7a62-44ed-a80d-3182d74e13e9",
      "cw-072b0972-0eaa-4d26-9897-a9ab5cd8e818"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-c302888b-e8cd-4274-9512-65beeeeb211a",
    "manifestId": "/api/digital_items/111616/2/manifest.json/",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "annotations",
    "thumbnailNavigationId": "cw-072b0972-0eaa-4d26-9897-a9ab5cd8e818",
    "thumbnailNavigationPosition": "off",
    "loadedManifest": "/api/digital_items/111616/2/manifest.json/",
    "canvasIndex": 0
  }
}