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/1073/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-a7b48312-cc28-4a37-98fe-6d8bde82e5d5",
      "cw-38eaef9c-cf0d-480a-80a1-588828da049a"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-15e47582-e522-491b-af0f-4f7d9facc0ae",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1073/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-38eaef9c-cf0d-480a-80a1-588828da049a"
  }
}