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/984/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0317d57d-0399-4b1f-9c96-276676c17fe5",
      "cw-8794217c-af5a-49a6-9d36-a45fc227b940"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-982b4bbd-1715-4d4d-a5fd-8dd190fa8f0c",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/984/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-8794217c-af5a-49a6-9d36-a45fc227b940"
  }
}