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/994/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-a1424a58-190c-4c1c-9aae-5fbea4fff55b",
      "cw-6c686dbf-e614-49f4-a8ab-2eec009160ed"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-8436e404-8a3d-4ef6-868f-e37e28d4572f",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/994/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-6c686dbf-e614-49f4-a8ab-2eec009160ed"
  }
}