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/maps1/9810/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-3216e287-0f2c-4362-b162-b4a96162529d",
      "cw-351f386a-04a7-4103-a660-ca8fa92e13f5"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-32a616b9-071d-4e2a-9964-6039a254e800",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/9810/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-351f386a-04a7-4103-a660-ca8fa92e13f5"
  }
}