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/884/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-350a0dbb-1c8c-4e22-9c0c-11d9af2f3a9b",
      "cw-140a5b87-a5f8-405f-955f-ba3cba2f8c91"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-bf9be534-893e-4f40-839c-e7e37dbf34b0",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/884/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-140a5b87-a5f8-405f-955f-ba3cba2f8c91"
  }
}