DI is probably floating, so any information may be sent to the RS-485 bus while DE is high.
That might mean that the hardware is less probably the source of your problems. My guess is a wrong configuration on the energy meter side. Triple check that. Don't miss any configuration option that relates to the external communication.
Sir, sorry to ask again but how to verify if DI is floating or not?
The energy meter settings are done as per this manual link. As far as I see there is no specific settings/configuration related to external communication
Parameter 13, 14 and 15 are definitely relevant. Parameter 16 is rather special as the Modbus protocol doesn't specify any authentication. Check that in the manual!
Either one of the RS-485 adaptors are faulty or the TX pin of the UNO, the DE pin of the UNO or the RX pin of the Mega is damaged.
In this context I checked the voltage levels of RS485 converters of both master and slave.At Master SideThe Voltage levels on pins are (w.r.t GND):DI - 5.00VRO- 5.00VDE & RE jumpered together- 0.0VAt Slave SideDI - 5.00VRO- 5.00VDE & RE jumpered together- 0.0V
That doesn't tell anything, unfortunately.