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/maps1/9294/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-6a2d2dd3-76f9-40c3-996f-2928dd770997",
      "cw-c50fddd2-7882-49f7-bb1a-a11263fac9a4"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-47607023-cd79-4f35-b8db-bb72335e692e",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/9294/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-c50fddd2-7882-49f7-bb1a-a11263fac9a4"
  }
}