DFRobot SIM7000E Shield - Opening serial ports issue

We tried to Interface with AT Commands in DFRobot SIM7000E Shield directly without any board. For that we used FT232L USB to TTL Converter

Our connection was as follows :
Tx of TTL Convertor - (D1) Tx of DFRobot shield
Rx of TTL Convertor - (D0) Rx of DFRobot Sheild
VCC of TTL Convertor - Vin of DFRobot Shield
GND of TTL Convertor - GND of DFRobot Shield

We tried on D0-D1 mode and D7-D8 Mode
in D0 D1 Mode
D0 - Rx
D1 - Tx
D7-D8
D7 - Rx
D8 - Tx
While opening the serial port in Serial terminal. we are not getting AT Commands response from the DFRobot sheid
when we press BOOT Button at that time we are getting print statements as like +CPIN : READY +CFUN : 1 SMS READY But at the same time while typing AT we are not getting any response from the Board.

Whether this is our Connection Problem ? Any help will much appreciated.