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/910/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-fb4a975e-88bb-4344-8b8d-90d948218baa",
      "cw-092ca370-996a-4c90-a87b-4e7e38394528"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-ed7bc0f3-d030-4037-b20b-e578c996dfe4",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/910/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-092ca370-996a-4c90-a87b-4e7e38394528"
  }
}