Hi Jesus,
The libpng warning is unrelated. You can ignore that.
The reason no shapefiles are exported is because there’s no topologies in the data you’ve loaded (and it looks like you’re exporting topologies). Maybe try the Reconstructed Geometries export instead.
Also it looks like you’re exporting colour rasters but that won’t export the filled polygons that I see in your screenshot. There’s not currently an easy way to do that - have a look at this thread for a non-ideal solution using the Image (screenshot) export.