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/1113/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-fc798617-ab0d-46a1-bcb1-e4e5d3a08b24",
      "cw-c1ff75e6-6e8c-4dbd-8b5e-b3a36979d944"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-25689ed1-9dc3-4725-9840-5424c391233f",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1113/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-c1ff75e6-6e8c-4dbd-8b5e-b3a36979d944"
  }
}