TypeError: Failed to fetch

{
  "manifest": {
    "error": "TypeError: Failed to fetch",
    "id": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/357/manifest",
    "isFetching": false
  },
  "window": {
    "autoScrollAnnotationList": true,
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-21ddcb42-fee6-412f-b97e-168e82f7f71f",
      "cw-78d15b76-abc7-4fe9-828b-e8f4ff102cd9"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-142b0abf-721c-484a-9f48-44af82c76ee6",
    "manifestId": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/357/manifest",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-78d15b76-abc7-4fe9-828b-e8f4ff102cd9",
    "loadedManifest": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/357/manifest"
  }
}