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/1076/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-c39e98f0-2878-4e89-8c1f-0db997eac7ac",
      "cw-cc2f9455-4f50-41a9-9bdc-ae87c7ff8cd0"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-f37b64bf-e0be-4cb2-84ad-d294083650f1",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1076/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-cc2f9455-4f50-41a9-9bdc-ae87c7ff8cd0"
  }
}