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/maps1/13268/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-e0321bf8-d741-4341-ada6-a08c5ead75f5",
      "cw-fe3da4d0-f71a-4b64-b18f-fc93a679a96d"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-1cc0f44b-9316-4f13-8ed9-940178f37a94",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/13268/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-fe3da4d0-f71a-4b64-b18f-fc93a679a96d"
  }
}