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/1038/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-dd6e3d9e-0a5f-4b92-a9b5-1fad1811eba2",
      "cw-5735813d-d936-4ea3-aa89-a1f8b59074e9"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-05f37c7a-f25c-480f-b433-44c48a8af7b0",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1038/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-5735813d-d936-4ea3-aa89-a1f8b59074e9"
  }
}