Tiff with transparencies show background black

Hi,
I'm trying to upload a geotiff tile with transparency, parts of the tiff with transparent background is showing as a black background. i have tried with the web account and with the classic studio but the results are the same. Also tried changing the style according to some solutions i read on forums but the results are still the same. i'm wondering what am i doing wrong?

on the other hand, i have tried with the next line of code of gdal [gdalwarp -t_srs EPSG:3857 input.tif output.tif] , this create a tiff with more than 400 mb, once i upload this one to Mapbox it still has the black background. the only application showing the tiff with transparent background is TileMill but once it is exported it takes so much time to generate the file, the mbtiles generated weight 5 gb and it is not uploading to MapBox. could you tell me if there is any other way to achieve this?

Regards


Start by reproducing the transparency behavior with the attached GeoTIFF and the reported GDAL command, then compare the uploaded result with TileMill's rendering. Done means identifying a supported way to preserve transparent pixels in the Mapbox upload path or documenting that the current path cannot do so.

Written by the indexing model from the issue text.