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/736/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-03aee617-e1db-40ed-8f21-8a13d8d043d9",
      "cw-a1dec9c5-0aa4-482f-a4c5-43bf2bff4f9d"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-b446aaf2-e244-4313-bce9-c3707fcd47b5",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/736/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a1dec9c5-0aa4-482f-a4c5-43bf2bff4f9d"
  }
}