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/706/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-205d30b7-ce1c-436f-9a21-17e814b427f3",
      "cw-6be9599d-2eab-4986-81f2-4354be2c9344"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-0d7ed2f3-c9d8-4d6f-b6c7-360271778ced",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/706/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-6be9599d-2eab-4986-81f2-4354be2c9344"
  }
}