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/maps1/10654/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0b57b94b-5be1-449d-98f1-34adf7be120a",
      "cw-b2dd3c4e-9293-4c30-993e-b754e5ed030e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5fd46130-1e35-429a-8830-79754cf44e95",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/10654/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-b2dd3c4e-9293-4c30-993e-b754e5ed030e"
  }
}