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/883/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-f06f4a9b-136d-4349-b2c0-decda4029c6a",
      "cw-5b254f31-4c2f-49f6-aa4f-0ef18375dd69"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-d9d2cf2b-1a72-42c1-bc3c-9970cc6b6253",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/883/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-5b254f31-4c2f-49f6-aa4f-0ef18375dd69"
  }
}