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/994/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-97237c19-4cdd-43b3-84d9-da1b856ac08b",
      "cw-62a61aa5-07eb-439a-b383-2934b1903faa"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5b1989b6-49f1-4df9-89d9-69b3360dee8b",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/994/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-62a61aa5-07eb-439a-b383-2934b1903faa"
  }
}