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/1145/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-6a1e9415-ec97-441e-ad2e-f18f5f015200",
      "cw-08f3b2bd-dc66-4b5c-ba4e-6d66fc0f6d2e"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-708a161f-054b-4311-8803-142b1d692717",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1145/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-08f3b2bd-dc66-4b5c-ba4e-6d66fc0f6d2e"
  }
}