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/734/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-bc39d66d-a8aa-478a-b332-8edcb056818c",
      "cw-35d1eb91-55d6-4f3a-9475-aa46f1c9a764"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-c76e7de9-32d9-404e-aaac-a44088098410",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/734/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-35d1eb91-55d6-4f3a-9475-aa46f1c9a764"
  }
}