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/752/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-8be3a308-fc94-4547-b46d-afcf708fa27e",
      "cw-4d0d8928-0717-4c97-962b-579d4f69f2cf"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-ff43bbad-ac09-4967-b752-c79148b92206",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/752/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-4d0d8928-0717-4c97-962b-579d4f69f2cf"
  }
}