Mirador viewer

SyntaxError: Unexpected token '<', "<br />
<b>"... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<br />\n<b>\"... is not valid JSON",
    "id": "https://iiif.rbge.org.uk/herb/iiif/E00001019/manifest",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-7156e658-575a-49c2-98ed-5d1f7eb6af94",
      "cw-784fd05c-00ba-43b3-98be-493f309d6833"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-dfc4d615-e036-4439-8645-808f7ca7c71e",
    "manifestId": "https://iiif.rbge.org.uk/herb/iiif/E00001019/manifest",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-784fd05c-00ba-43b3-98be-493f309d6833"
  }
}