Earthdata Forum

Please, I have a problem opening monthly Modis-aqua in Seadas (win10). The following error appears "No appropriate product reader found". The old naming files are usually opening.

Can you share the specific name of the file that SeaDAS failed to open?

Sure.
AQUA_MODIS20180220.L3b.DAY.CHL.nc
AQUA.MODIS.20210201_20210228.L3b.MO.CHL.nc
I downloaded these files just to test because some students had problems opening some files.

These could be typos on the forum post, but I see errors in the filenames you are using.
AQUA_MODIS20180220.L3b.DAY.CHL.nc should be --> AQUA_MODIS.20180220.L3b.DAY.CHL.nc
AQUA.MODIS.20210201_20210228.L3b.MO.CHL.nc should be --> AQUA_MODIS.20210201_20210228.L3b.MO.CHL.nc

SeaDAS no longer provides a reader for L3b files, even with the old naming convention. You can use l3mapgen to create L3m files from L3b, which SeaDAS can read -- https://seadas.gsfc.nasa.gov/help-8.2.0/processors/ProcessL3mapgen.html

Or you can download the L3m files here --
AQUA_MODIS.20180220.L3m.DAY.CHL.chlor_a.4km.nc
https://oceandata.sci.gsfc.nasa.gov/directdataaccess/Level-3%20Mapped/Aqua-MODIS/2018/051/
AQUA_MODIS.20180201_20180228.L3m.MO.CHL.chlor_a.4km.nc
https://oceandata.sci.gsfc.nasa.gov/directdataaccess/Level-3%20Mapped/Aqua-MODIS/2018/032/

Ok. Thank you for your attention.