flock with crontab is not working properly

I have a crontab job, that looks like this:

*/5 * * * *  /usr/bin/flock -w 0 /home/partners_perfluence_delivery/cron.lock cd /home/partners_perfluence_delivery && /usr/bin/python3 /home/partners_perfluence_delivery/main.py

When I run script main.py manually, everything works like a charm. When I'am trying to use crontab job, lock-file is created, but when I am looking for a job with ps aux | grep main.py I see nothing in the output as well as requests used in main.py are not being made

What am I possibly doing wrong?