Suricata

I use suricata 4.0.4 and in suricata.yaml, i edited fast.log and files-json.log to enabled:yes - append:yes. But when I cat fast.log and files-json.log, files-json.log is empty.

Is there any way to solve this problem? Thank you very much.

I would recommend using latest stable Suricata - 4.1.4 and eve.json (instead of fast.log and files log as these are legacy).
After it is up and running , check if Suricata starts properly , if there are no errors , if you have defined your networks correctly.