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/maps1/30218/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-cc5d5426-587e-420d-8cb8-4b6e7a612dbc",
      "cw-7e0e3c23-5ebe-47cc-938d-23373e9cb05e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5d1cf422-1778-401a-9efe-ac96422eab34",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/30218/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-7e0e3c23-5ebe-47cc-938d-23373e9cb05e"
  }
}