DSI_UNSAccountB_Delete process not triggered after execution of account deletion

Hello all, 

Here is the context of this issue : 

- we created a new synchronization project (Native Database Connector - SQL Server) to manage user account deletion on a target system (SQL DB). User accounts are synchronized in UNSAccountB table and we created a dedicated custom target system for that. 

- The user account deletion is done by executing a store procedure the system owner provided us. Except that, we have a read only authorization in the system. 

- We didn't user default templates to create the synchronization project and we realized we were missing dependencies for this project (especially Single Object Operations in the Designer to trigger DSI_UNSAccountB_Delete process)

--> so we created one dedicated to our target system and we named it 'Delete'

- We also created a dedicated workflow in the synchronization project only for Deletion, with Synchronization Direction = Target System

- We realized also that we had to define our target system type as 'DB' to meet one of the requirements of the pre-script for generating DSI_UNSAccountB_Delete.

But even after all those checks, the process DSI_UNSAccountB_Delete is still not triggered when we execute the account deletion in the deferred operations.  So we weren't able yet to test the store procedure execution. 

Would you have an idea of what we are missing ? 
We also tried to use AdHoc Single Object Operation but still not working

We are using version : 8.1.4

Thank you for your help,

Olivier.