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/maps1/27211/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-8acda7c1-6a4d-4788-a3a8-b8f865e098ba",
      "cw-7369349d-27ac-4d7f-83ec-58effd4f05c8"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-14418c36-cc3c-4073-bb74-c0838b9428e4",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/27211/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-7369349d-27ac-4d7f-83ec-58effd4f05c8"
  }
}