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/maps1/22254/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-10bd768d-45f3-4d48-b265-47beb4f34e38",
      "cw-f9b91907-c035-4401-bdab-522dfa206f58"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-86885dd3-a486-4803-bef4-a188910e8934",
    "manifestId": "https://digital.libraries.psu.edu/iiif/info/maps1/22254/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-f9b91907-c035-4401-bdab-522dfa206f58"
  }
}