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/636/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-67065b52-0430-4847-b3f8-457727beb827",
      "cw-f33d015e-5fb1-4226-890f-c54f321d686f"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-f2b769c5-f85d-460c-845c-415cb0a58ae8",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/636/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-f33d015e-5fb1-4226-890f-c54f321d686f"
  }
}