Mirador viewer

SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "https://digital.libraries.psu.edu/iiif/info/maps1/2234/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-7bfe837f-f21c-4a19-9ba3-915d8887c2ee",
      "cw-95ac27cf-ce15-4d24-83b6-68880738b09d"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5b1a3d78-005d-4e27-ad59-7ae11dcf0839",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/2234/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-95ac27cf-ce15-4d24-83b6-68880738b09d"
  }
}