Mirador viewer

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

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1119/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-6385fafa-1bd7-4651-bc3e-083d9d29e134",
      "cw-87e0f460-8d27-44b1-b66f-742d231358b9"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-2aa5ab84-3ed5-4f7d-ab2f-d95c0e2a9de9",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1119/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-87e0f460-8d27-44b1-b66f-742d231358b9"
  }
}