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/maps1/16209/manifest.json",
    "isFetching": false
  },
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    "highlightAllAnnotations": false,
    "id": "window-990a39e6-a234-4e20-8753-57435534b5fb",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/16209/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-c7dcffa1-e7a1-4920-a499-4afede3cbd4b"
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