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/1150/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-446cac28-ebb1-4ded-99e1-06da2797b975",
      "cw-e7b89f3f-5fdf-46bb-85d7-3d01cd40f1a7"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5899ffe1-0d79-466d-8171-c5b6ba2751f5",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1150/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-e7b89f3f-5fdf-46bb-85d7-3d01cd40f1a7"
  }
}