As many of you have seen we launched our Google Sites Classic Comparison earlier this week, thank you for all the feedback! It comes as a surprise, however, that we can see an update to new Google Sites so quickly, but many of you may see the update as actually removing a feature in an attempt to fix it. It's fantastic to see Google actively working on new Google Sites so we look forward to what else is in store.
We reported in the Google Sites Help Forum that the Upload feature behaved strangely in that if you upload a file then that file is not share correctly from Drive and therefore cannot be seen in a published site. We then saw further reports that files could no longer be uploaded at all, so we asked for confirmation if this was the intended behaviour and await a response. This means that the upload feature can now only upload images, which the images feature already provides, rendering the upload feature a simplified version of the images feature. Do you see the same behaviour? If you do then please send feedback to the Google Sites team or add your own experience to the Google Sites Help Forum.
This means that you need to use Drive to upload files to, share the files appropriately and then link to or embed in your site.