After a lot of hours of searching, I finaly made it work!! The other application's crash had nothing to do with FOP2 and it was just a bad coincidence that happend when I activated the FOP2. So I focused on the problem that a user's extension could not log in if it was used from the other application. On my lab,everything worked perfect, but at my customers PBX, I still had the same behaviour. Finally I commented the #exec line and programmed everything from the scratch on buttons.cfg and it wotked!! I still do not know why the freepbx autoconfig did not worked. Maybe a system restart could have fixed the problem...
Anyway, I would like to thank you for your instant reply and the support and all your efforts!!

Best regards

I successfully installed an licensed version of FOP2 in an Elastix Server 2.4.0 . The customer has another application that uses a Manager Interface that receives information from the PBX provides CRM on terminal PC's. The extension by the terminal PC is registered on the program and when someone calls the agent, a pop up window provides information for the caller, as well the agent can click-to-dial from that program using his telephone. The problem is that for some reason, I can not login in FOP2 web interface of an extension, if the extension is used by the other program. If the extension is not used by the other program, everything works OK with FOP2. Meanwhile, when FOP2 is enabled, the other application stop working. The question is if FOP2 can run simultaneously with another application that does somehow the same with FOP2.