I did not receive performance fee last month --- why?

I am providing strategies and some people are copying me in May. But I did not received any performance fees from my copiers. I am sure that they have made profits, because all may trades are winning trades. It says that the performance fees will be paid at the end of the calculation period (one month).

Does this mean the performance fee will be paid by the end of each calendar month? Or does it mean the performance fee will be paid one month, after the copier started copying my strategy?

Could any help?