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/maps1/3434/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-3e8a70d0-1426-4329-b9d2-41ad86ad3975",
      "cw-62715019-42d1-4703-beec-9d0ca32d4ebb"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-051cd953-1f14-4219-82b5-6707fdd284b1",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/3434/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-62715019-42d1-4703-beec-9d0ca32d4ebb"
  }
}