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/maps1/30131/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-ab5b861e-af80-40fe-ab90-6405f3ffd956",
      "cw-c11795c6-db5d-49f0-b342-e4ce362696e5"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a068006c-0642-4dac-92b6-a38a3ce7c351",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/30131/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-c11795c6-db5d-49f0-b342-e4ce362696e5"
  }
}