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/maps1/23130/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-9d54d4a0-87a5-489d-9839-3000005b82f7",
      "cw-280a50a6-1928-4cb8-981e-16500748f5ec"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-122f6b09-b837-4fe3-bda7-deabf0d2925b",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/23130/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-280a50a6-1928-4cb8-981e-16500748f5ec"
  }
}