Continous failing of this test with title -confirm client server communication

I am easily able to tranfser files between desktop and mobile and i am pretty sure my all steps are correct but still I am getting a failure in assessment in this test.Please help

Please perform the transfer of files to filezilla as well, both upload and download.

I have already done that.I have sucessfully transferred jpg files from mobile client to desktop client and vice versa.Also /i have transferred upload.txt to ftp_server and downloaded download.txt to ftp_client directory

I have seen your log file and it is clear that no communication happened between the server and client in the workspace (Internal client server communication).

What should i do now.
I am unable to understand this.

What ever activity that you do with the server is stored in vsftpd.log file. It maintains a log of all the activities performed by the user. That file is used to evaluate if a user has started a server, done file transfer or not. What i can suggest is, try to do a file transfer through your workspace (Internal file transfer). After you have done it, check the log file that if everything is recorded correctly or not. If everything is recorded correctly then you will pass the assessment.
If you cannot generate a log file, there are many questions regarding this on the forum, please go through it if you cannot generate a log file.