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/maps1/12334/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-84963c2b-ab3a-42c2-b0a2-1163c03b4752",
      "cw-8aa1c758-793b-480f-9061-b45d552d7969"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-c95dcd68-846c-42ae-9c1c-dd43bd0bed07",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/12334/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-8aa1c758-793b-480f-9061-b45d552d7969"
  }
}