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/maps1/25064/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-7f0b52f5-cac6-4dbd-a07e-1ff442579875",
      "cw-2dbc0039-b347-4a02-a45b-d9e3bcb70873"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-f559d723-905d-45c5-ba52-73cee06da149",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/25064/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-2dbc0039-b347-4a02-a45b-d9e3bcb70873"
  }
}