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/655/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-e0d54db1-d2ed-4497-b636-3c3ad5ba8605",
      "cw-4d31b5cf-6e21-4492-8d53-031b3914fd48"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-f0397937-3aa1-4439-8f62-edfb99cf6f24",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/655/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-4d31b5cf-6e21-4492-8d53-031b3914fd48"
  }
}