TypeError: Failed to fetch

{
  "manifest": {
    "error": "TypeError: Failed to fetch",
    "id": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/494/manifest",
    "isFetching": false
  },
  "window": {
    "autoScrollAnnotationList": true,
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-f886f931-0304-4c4a-b5fa-3470ba9c4f0e",
      "cw-bede004b-80f7-4cfa-b97d-5998da60887a"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-b9748e64-334c-449a-9d87-b134c5eebaf6",
    "manifestId": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/494/manifest",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-bede004b-80f7-4cfa-b97d-5998da60887a",
    "loadedManifest": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/494/manifest"
  }
}