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/962/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0c022a68-8aa0-424b-9118-99c4613ea6b4",
      "cw-7b2c4d70-5031-42b2-bf23-a9063db9b335"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a611aeb1-3f73-48e2-a7d1-8a01f63f60b9",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/962/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-7b2c4d70-5031-42b2-bf23-a9063db9b335"
  }
}