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/maps1/26834/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-22584ba0-4902-47da-9a7d-bb2aa8cd3ce0",
      "cw-80927aa2-43d2-473f-8880-ef40b4a98a2a"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-3b468154-7c34-42a4-996f-b7147ff6ba5b",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/26834/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-80927aa2-43d2-473f-8880-ef40b4a98a2a"
  }
}