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/maps1/26768/manifest.json",
    "isFetching": false
  },
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    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-8b53b578-9c64-43c9-a8d7-af4b1ace8981",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/26768/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-7d0a983e-afb7-4cd4-bfc4-17bfc2b5caae"
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