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/maps1/30124/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-261faabf-9d61-43b7-8c65-397f81ba2389",
      "cw-d8158ec7-9220-4fa2-8872-1cfa15b51381"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-b4368afa-cc69-4390-91bb-646a9e62fd69",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/30124/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-d8158ec7-9220-4fa2-8872-1cfa15b51381"
  }
}