Mirador viewer

SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
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    "isFetching": false
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    "highlightAllAnnotations": false,
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    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/4996/manifest.json",
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    "rangeId": null,
    "rotation": null,
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    "sideBarPanel": "info",
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