I notice that the electrical technician connected a neutral line of new energy meter installed in our building to the loads connected to old energy meter .
Is there any problem may occure due to what i said ×.×
There is no problem likely if, and only if, the rest of the wiring is in conformance to the electrical code used here in the USA. In some other parts of the world electrical wiring and connections may be different. Normally all neutral connections should be at the same voltage, fairly close to zero. And in many areas all neutral circuits must be tied to each other.
That may not be advisable in some other parts of the world.