I have no problem executing this statement on my end. Do you get an error message? What's the error? And if you do receive an error, are you able to view "0#BUYSELL.SZ" in a Quote app in Eikon?
If what you meant is that the call returns the data with no errors, but the data is not what you expect, i.e. it's not the constituents of the chain, but the chain itself, then try
instead, which does return the chain constituents.