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/maps1/10000/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-96c00d34-830f-4e2a-b835-692c7e787d14",
      "cw-de1e2313-e372-479e-98f2-a45add8384c8"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-0c79d31b-a325-4a8b-bcfd-4d08c4be5c99",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/10000/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-de1e2313-e372-479e-98f2-a45add8384c8"
  }
}