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/885/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-a24cc704-76b7-40e3-96b0-35629501f9cd",
      "cw-30559c4a-d3a3-4e95-909f-c98c7fd389ef"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-85fb37e9-d683-4c0c-b65d-c83bb2c2a9c1",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/885/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-30559c4a-d3a3-4e95-909f-c98c7fd389ef"
  }
}