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/maps1/29715/manifest.json",
    "isFetching": false
  },
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    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-13f7f868-880a-44b1-88f6-184261be68b4",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/29715/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-564502b1-9b4c-48f3-b0e6-65c6d50f2daa"
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