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/maps1/24263/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-598b6402-1a5c-4768-a59a-32025d1f3e34",
      "cw-56a9f962-237d-440b-93e7-fc3502007580"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-58f99ec3-7022-475e-8eeb-0650e8dd70b3",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/24263/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-56a9f962-237d-440b-93e7-fc3502007580"
  }
}