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/616/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-16bcca13-4a55-45a8-8aa6-15b2856dc251",
      "cw-c48fd20f-666f-4047-aafc-858a205c54d2"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-cb50efda-442e-4a62-b363-f01e3b2549a2",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/616/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-c48fd20f-666f-4047-aafc-858a205c54d2"
  }
}