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/674/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-b00a9f7f-9e2c-4939-9df2-927472947911",
      "cw-debb6e35-817e-4c09-96cc-25c5368e8cce"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-b88f00d0-11a8-4333-8ac1-15332addf3f5",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/674/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-debb6e35-817e-4c09-96cc-25c5368e8cce"
  }
}