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/1176/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0768e2d3-f9f4-4cf8-af4a-9db5b372eb3e",
      "cw-91905b43-478f-4595-ab89-8e0ea4a18f6e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-6d61c40f-5411-45ee-b6f7-cda4c9e461d0",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1176/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-91905b43-478f-4595-ab89-8e0ea4a18f6e"
  }
}