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/maps1/5257/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-d9da7544-ca26-4b6d-9ac9-a47d6a8d451a",
      "cw-d1bbc56f-aa98-49f2-90bb-3796df0b2e37"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-6a5be22f-bff3-4cd4-8f00-f8d6f4af38b2",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/5257/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-d1bbc56f-aa98-49f2-90bb-3796df0b2e37"
  }
}