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/700/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-cc93a2ab-2a52-4406-b406-ee9f9733fa24",
      "cw-7af05de5-2cd3-4752-b7e1-95a3342ba952"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-c3e92950-d291-4e0a-894c-534d506e9286",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/700/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-7af05de5-2cd3-4752-b7e1-95a3342ba952"
  }
}