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/677/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-971f1311-a4ea-4079-9e0e-db77dbe25745",
      "cw-a804c826-14b1-48e6-b931-a868d1dc7892"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-7419955b-4378-43f4-b67e-18746ba93a17",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/677/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a804c826-14b1-48e6-b931-a868d1dc7892"
  }
}