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/maps1/24392/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-b3216628-6ebf-4c64-bc40-4f627b48a98f",
      "cw-40faa8ed-8dfe-490a-864a-dee983be1317"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-baf92c7c-1221-4595-852c-ffac44640f75",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/24392/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-40faa8ed-8dfe-490a-864a-dee983be1317"
  }
}