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/1026/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-cfe1c2ce-dfb4-4196-8e6c-da74ff8f1ff6",
      "cw-8348b475-c840-416b-97f6-e1145bbba4bc"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-589c3273-8e67-408b-aff8-813582341207",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1026/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-8348b475-c840-416b-97f6-e1145bbba4bc"
  }
}