You need to include more details to get appropriate help, but here are some general things to confirm.
Wiring
You should use a 3 wires to connect the two devices together (preferrably RS-485 rated cabling, 1.5 twisted pair conductors - the .5 is for the 3rd wire for common-mode reference).
The devices should be wired as follows:
HC 003 67
MB3180
A / -
Data- (Pin 4 on the DB9)
B / +
Data+ (Pin 3 on the DB9)
GND
GND (Pin 5 on the DB9)
Configuration Settings
The baud rate, parity, and stop bits must be the same for both devices.
The MB3180's serial port must be configured for RS-485 2 wire.
The MB3180 must be configured for RTU Slave operation mode (meaning it is actually the master on the bus and will be communicating to Modbus RTU slave(s) connected to the serial port).
The slave address configured on the HC 003 67 must be the same as the targeted address by the MB3180 (which directly corresponds to the Unit ID in the Modbus/TCP request from your client, assuming you're using the MB3180 to connect the HC 003 67 to a Modbus/TCP client).
Confirm that the MB3180's Response Time-out setting is sufficiently long. Try setting it to 2000ms (2 seconds) or more to be sure or use the Auto Detection feature.