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/951/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-97cd44c1-bf36-4958-ad12-817df68e7209",
      "cw-be14259b-ac4b-409a-ba1c-7725bd153506"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-2e9d3042-0512-4fa6-b24f-d728f074df91",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/951/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-be14259b-ac4b-409a-ba1c-7725bd153506"
  }
}