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/1072/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-85a55ba9-ed29-4963-b0e1-bc52971a3ad9",
      "cw-abb45fd6-38d1-4472-bdf1-f6606732a30a"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-9223a803-5d1e-4774-b0bb-131e423cefe1",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1072/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-abb45fd6-38d1-4472-bdf1-f6606732a30a"
  }
}