I think it hasn’t worked properly since the last update, both in the Mac App and in the web.
Is this a known issue?
1 Like
Hey Jose!
We are indeed aware of an issue with Set as thumbnail not working under certain circumstances. Would you mind wrting to us (productsupport@sketch.com) so we can add your details to the report and let you know as soon as it is fixed? 
While we look into it, there’s a workaround: make sure you have set the artboard as a thumbnail (select it, then right-click → Set as Thumbnail) and make a change, like adding a new layer (you can remove it later) and that will get you the right thumbnail.
1 Like