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/624/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-792a85ad-003d-42aa-9976-0e7638a9fc46",
      "cw-d9e58e38-8f6d-4274-ac0c-23c73c9b1666"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a7cff850-ba12-42d0-bbaa-ecef9083a731",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/624/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-d9e58e38-8f6d-4274-ac0c-23c73c9b1666"
  }
}