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/632/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-1ea42344-93fd-4f86-9c5d-60a9a14be644",
      "cw-0fcb9b11-a9af-446f-ba19-118f790eb918"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-39d061f9-96be-4fad-b121-7580f0c6a70d",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/632/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-0fcb9b11-a9af-446f-ba19-118f790eb918"
  }
}