Have a look as well at this question, it might helphttps://knowledge.safe.com/questions/68502/fme-server-featurewriter-transformer-role-in-data.html
I think the problem might be the set-up of the Download Service.You have to set which writers are being included in the download in the service properties while publishing your workspace:
Beside that, you're using FME 2018.1.1 and in that version the Download Service couldn't use output data from FeatureWriters.This has been solved in FME 2019:https://knowledge.safe.com/idea/41306/use-featurewriter-output-for-datadownload-service.html