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/maps1/2029/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-2117f5ea-ced2-45ca-9a71-83723df267ab",
      "cw-100d10fd-dcdc-462d-9d93-650ca5d1609b"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a675a540-4e5e-474c-a847-66bda6956764",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/2029/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-100d10fd-dcdc-462d-9d93-650ca5d1609b"
  }
}