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/704/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0c3e1430-bad8-4def-aa31-9ec5110128ba",
      "cw-8cc2c17c-2ff5-41d2-b011-d4224dd50476"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-f8b1253b-9345-4a0b-9892-320fc65a4ca2",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/704/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-8cc2c17c-2ff5-41d2-b011-d4224dd50476"
  }
}