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/maps1/27872/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-9c3f2aba-3830-404d-b542-640b9986d450",
      "cw-f2117ce8-c2c9-47cf-bc4b-01727374fbdd"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-b6d24233-6bbc-4b9a-9d6d-7a966b33a1a9",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/27872/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-f2117ce8-c2c9-47cf-bc4b-01727374fbdd"
  }
}