TypeError: Failed to fetch

{
  "manifest": {
    "error": "TypeError: Failed to fetch",
    "id": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/749/manifest",
    "isFetching": false
  },
  "window": {
    "autoScrollAnnotationList": true,
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-f93c0c62-edef-4405-a12e-d6924abc4a1a",
      "cw-a28ae145-2ca7-410c-adf8-6a86aa60cda0"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-a9301613-47c4-43fe-8a96-affc20eb7e07",
    "manifestId": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/749/manifest",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a28ae145-2ca7-410c-adf8-6a86aa60cda0",
    "loadedManifest": "http://jaegerstaetter-test.literaturtirol.at/omekas/iiif/2/749/manifest"
  }
}