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/649/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-be458143-f669-4940-8cbb-5d26d014ddf7",
      "cw-6b0305b7-1408-4f58-b543-6f7ec8ec606f"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-af09aca0-509b-4601-813b-c80aea065044",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/649/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-6b0305b7-1408-4f58-b543-6f7ec8ec606f"
  }
}