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/maps1/2410/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-84c26da6-f6bd-4e9a-b170-245c7a826336",
      "cw-8544b87f-81f5-4d30-b7b9-064ee45f1be7"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-84a5f55d-9a8d-4a52-86c6-9fc0410f73db",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/2410/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-8544b87f-81f5-4d30-b7b9-064ee45f1be7"
  }
}