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/611/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-e0156f85-3607-4caf-a41c-478cfbce309a",
      "cw-dd2d0cb3-4aa5-41b7-aa21-eaef656cc40e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-0cff4c01-3b42-44a4-ba52-f3602a5a439c",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/611/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-dd2d0cb3-4aa5-41b7-aa21-eaef656cc40e"
  }
}