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/maps1/24872/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-5e563b52-6795-4d84-96c9-8f3e545ec0e7",
      "cw-d9db5993-cae1-4302-8006-5693019f33be"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-42e67d4c-170d-4103-a906-168646e99db0",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/24872/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-d9db5993-cae1-4302-8006-5693019f33be"
  }
}