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/624/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-b920b2cc-5166-4989-adf1-b46e7e8935ed",
      "cw-a4f1f80a-2955-41dd-a572-cef54f0ae8cf"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-cf5d59e3-360f-4867-a6cf-7c160c2eedf0",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/624/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a4f1f80a-2955-41dd-a572-cef54f0ae8cf"
  }
}