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/maps1/29034/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-2d9f2c0b-76f0-4095-8a3c-5a83506ef5d0",
      "cw-2973d16c-99b8-4138-a335-81d799c31075"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-ecc6938d-28bb-43b0-93f6-b5fe50a6c6fd",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/29034/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-2973d16c-99b8-4138-a335-81d799c31075"
  }
}