Thanks DdlV for your answer.
Also I'm using Zorro with a 10-digit account for about 7 months and everything seems to work fine.
Last week I opened another 8-digit real account and Zorro regularly opened trades. But today I saw that Zorro tried open a trade without succeeding. This is why I would like to clarify this topic for me and others users.
The simplest solution is migrate to a new 10 digit account but I would like to know more about FXCM API.

thks a lot