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/662/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-41f80ef6-393c-4b45-9714-636dc99f0ddd",
      "cw-5792bacb-addf-460b-9fba-f0b6c918f052"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-31d56207-8acf-4a5e-83d0-3756d30abcd8",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/662/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-5792bacb-addf-460b-9fba-f0b6c918f052"
  }
}