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/maps1/24762/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-e25d4cbc-1a3a-4a07-8971-62358f2cc9eb",
      "cw-78ff8198-637a-40b3-ae07-c97e078ff7c0"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-d08b1410-a772-4d78-92a0-b61095a60b7b",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/24762/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-78ff8198-637a-40b3-ae07-c97e078ff7c0"
  }
}