I'm not sure I'm following you but try

WHERE NOT EXISTS (SELECT 1 FROM ManyToManyTable
 INNER JOIN ChildTable ON ManyToManyTable.NoChildTable=ChildTable.Numero 
 WHERE Master.Numero=ManyToManyTable.NoMaster
   AND ChildTable.Enabled <> 1 )

>Here is an example, where I added Sergey's logic in it:
>
>

>SELECT Master.Numero
>FROM (SELECT Master.Numero FROM Master 
>WHERE EXISTS (SELECT 1 FROM ManyToManyTable
> INNER JOIN ChildTable ON ManyToManyTable.NoChildTable=ChildTable.Numero 
> WHERE Master.Numero=ManyToManyTable.NoMaster
> HAVING COUNT(*)=SUM(CASE WHEN ChildTable.Enabled=1 THEN 1 ELSE 0 END))
>GROUP BY Master.Numero) Temp 
>INNER JOIN Master ON Temp.Numero=Master.Numero 
>