TypeError: Failed to fetch

{
  "manifest": {
    "error": "TypeError: Failed to fetch",
    "id": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/354/manifest",
    "isFetching": false
  },
  "window": {
    "autoScrollAnnotationList": true,
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-10cfeee7-de35-442d-94a5-7599aa184dc2",
      "cw-2ad19226-6a91-4419-a9e4-eac7c698b4c0"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-0e2bf29c-82da-4b71-acb5-9fc73d92aaed",
    "manifestId": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/354/manifest",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-2ad19226-6a91-4419-a9e4-eac7c698b4c0",
    "loadedManifest": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/354/manifest"
  }
}