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/maps1/7235/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-bcd1013e-bd21-4a8c-b365-fc89c6f74ade",
      "cw-95caeb27-df68-4206-a76b-529149a95271"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-c3892ad4-662d-4fdf-97f3-b2ea140229c5",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/7235/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-95caeb27-df68-4206-a76b-529149a95271"
  }
}