In ArcGIS Experience Builder, no data is previewed in the thumbnail when selecting the 'Create thumbnail from map' option when creating an app.

Workaround

1. Use ArcGIS Web AppBuilder instead of ArcGIS Experience Builder, which results in expected behavior when creating a thumbnail from a map.
2. Save the image of the desired thumbnail area from Map Viewer.
3. Select the image to populate the thumbnail using the Edit Thumbnail option to upload the image (600 x 400 or larger).

Steps to Reproduce