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/maps1/24854/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-07dd6358-7b75-4985-8d04-c872c2e2a04b",
      "cw-f551a903-1ed3-4224-bd4f-1a1da56ff73b"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-4612c303-4382-4934-a31e-4edb5086873f",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/24854/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-f551a903-1ed3-4224-bd4f-1a1da56ff73b"
  }
}