TypeError: Failed to fetch

{
  "manifest": {
    "error": "TypeError: Failed to fetch",
    "id": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/395/manifest",
    "isFetching": false
  },
  "window": {
    "autoScrollAnnotationList": true,
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-b4dd9105-0ad2-47c4-94d8-4b457cc3ed23",
      "cw-a61f59b2-c816-43d4-b83a-d7f9d0a84c91"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-51abcb47-c92d-41a9-a6b3-5af10399dd7d",
    "manifestId": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/395/manifest",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a61f59b2-c816-43d4-b83a-d7f9d0a84c91",
    "loadedManifest": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/395/manifest"
  }
}