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/maps1/11560/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-9e6ed00b-985a-468b-b7f0-be6f533b4006",
      "cw-8df4b04d-77f7-4606-b97f-626075249aae"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-aa8599a1-f261-4b5e-bb61-a18f4ddf35ed",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/11560/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-8df4b04d-77f7-4606-b97f-626075249aae"
  }
}