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/1074/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-662b8755-5710-43f6-8010-9480b446eced",
      "cw-4318007d-41ba-4f75-8d7c-1487b41f0b81"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5caaec57-caa1-459f-8f07-9478fd508344",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1074/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-4318007d-41ba-4f75-8d7c-1487b41f0b81"
  }
}