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/654/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0036f7d0-2ee2-44a6-95fc-cd8a2b5b2839",
      "cw-d0d16448-38bf-4309-8b98-204eb405d925"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a2849f6b-4fbc-4cbd-bce4-2972e9ff01d5",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/654/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-d0d16448-38bf-4309-8b98-204eb405d925"
  }
}