STLINK/V3 debugging problem with STM32 C series.

We are providing power to our Customised Microcontroller (STM#@ C series) board from my power supply@3.3v. we are using STLINK-V3SET with MB1440 adapter, it is an extension board provided by ST.
We have connected 3 PINS GND, SWDIO(PA13), SWDCLK(PA14) from CN6(connector 6) of extension MB1440 board. to our microcontroller board.
Getting above error.
NOTE: Clock used is internal & pinout as follows:

a) Is T_Vcc an i/p pin? Do we need to give input 3.3v from my microcontroller board to Debugger connector's CN6 T-VCC pin. When we checked no voltage is present on CN6 T_VCC pin.
(We are powering microcontroller board from external power supply, because 3.3v is not present on STLINK/V3 extension MB1440 board.
b) Do we need to connect NRST pin of CN6 extension MB1440 board to the Microcontroller board . We checked, its remaining high @3.3v on microcontroller board.
Thanks.
