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/maps1/30350/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-fefa1115-492c-4725-8312-c545f596ea02",
      "cw-0fed60e8-62cb-4a1c-abdf-e9ceed5ab8e5"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a221407f-21dc-41cf-b355-f81fb54fbf3e",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/30350/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-0fed60e8-62cb-4a1c-abdf-e9ceed5ab8e5"
  }
}