Hi Javier,
It seems you were trying to create bid invitation in SOCO.
And I think it should call function BBP_PD_BID_CREATE.
Please also try to set a breakpoint at FM BBP_RFQ_FROM_SOCO_CREATE.
Please make sure you set the external breakpoint for the user, who is performing this action in SRM portal.
In addition, if you have several servers, after you set the breakpoint, please use the transaction "/nsrdebug" to make sure the breakpoint will stop at all your servers.
Hope this could be of some help.
Regards,
Wendy