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/911/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-1b6e657c-af03-49a6-bacc-869b376fbf83",
      "cw-e4637e9d-232d-4e5b-9fdf-fa621b6a594d"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-920f5255-66b0-460e-b5d2-3c1e63430b79",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/911/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-e4637e9d-232d-4e5b-9fdf-fa621b6a594d"
  }
}