I download S3 L1 and I did atmospheric correction by using ICOR and I tried resampling then did reprojection but on the reprojection screen my source product product not read also even I tried to manual selection but it say source product not valid…?
If I remember correctly this is an issue of icor.
In SNAP you can go in the menu to “Tools / Attache Pixel GeoCoding” Afterwards the geo-information should be available.