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/693/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-4e909330-c6b3-465c-ad04-d113b35c917d",
      "cw-0cfec751-651b-4a9a-8630-3c31428bc43c"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-2338a0a8-4bad-4e08-bd0f-b21494967535",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/693/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-0cfec751-651b-4a9a-8630-3c31428bc43c"
  }
}