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/maps1/14642/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-e570386b-8737-44b4-bd62-36695ff025d6",
      "cw-576e4cbb-33ca-41ae-8aa6-f08fe8514733"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-17f85525-bf9c-457a-a448-8f3a6a22e592",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/14642/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-576e4cbb-33ca-41ae-8aa6-f08fe8514733"
  }
}