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/maps1/30283/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-7aef649d-9a08-4e62-a8d2-b83375e2d43e",
      "cw-34bb9340-b1c9-42ef-8f85-ace1838fcbbf"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-4a974195-a04e-4e58-8bd5-d31affdf9078",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/30283/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-34bb9340-b1c9-42ef-8f85-ace1838fcbbf"
  }
}