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/maps1/23296/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-4c3f79f5-2188-431c-bc00-462469f408fc",
      "cw-d443124b-efb2-466a-93c0-732162b066f6"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-366bf000-f23e-4f6a-8e44-5a59490bbcc1",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/23296/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-d443124b-efb2-466a-93c0-732162b066f6"
  }
}