Mirador viewer

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

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/898/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-de97b338-225d-4a58-859c-76cadbabbd90",
      "cw-4ddbb217-ae2a-401c-a204-28a1c36d4783"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a6048ff7-2e0f-405e-ac17-d05ce16b3100",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/898/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-4ddbb217-ae2a-401c-a204-28a1c36d4783"
  }
}