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/711/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-a7267750-29b1-47af-9f2a-c39b903bd9c3",
      "cw-09274ccf-4861-4669-9797-8e0ae5b6ede2"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-0fd70334-bf8e-44b2-ba83-f024bb928079",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/711/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-09274ccf-4861-4669-9797-8e0ae5b6ede2"
  }
}