TypeError: Failed to fetch

{
  "manifest": {
    "error": "TypeError: Failed to fetch",
    "id": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/435/manifest",
    "isFetching": false
  },
  "window": {
    "autoScrollAnnotationList": true,
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-8c4c4575-c18a-4771-885a-69c114a57a10",
      "cw-cf3e8c80-85c6-485c-a604-fd9d35ad6dff"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-cf0c48e1-9747-453b-814e-4cd69820ffbc",
    "manifestId": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/435/manifest",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-cf3e8c80-85c6-485c-a604-fd9d35ad6dff",
    "loadedManifest": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/435/manifest"
  }
}