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/697/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-2af405e5-73bf-4fe9-abb2-9c38645ad8fa",
      "cw-48529cfe-e743-4ea2-aff7-14b308b7094f"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-f276da57-78fa-4bf0-a8c8-76780bd74bdd",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/697/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-48529cfe-e743-4ea2-aff7-14b308b7094f"
  }
}