I am working with Nucleo-H743ZI2. Using ST Programmer I did full chip erase with Read protection option bytes as CC. Now am getting an error message cannot find STM32 target. I guess I have to reflash my basic firmware packages from ST but I am not aware how to do it since am using ST nucleo board newly. Any suggestions would be appreciated thanks in advance.
Setting the RDP (Read protection) to 0xCC means you have activated the RDP Level 2:
Then is going to be impossible to reduce the protection level.
That's why you need a new board now since this board is locked.
The ST Boot Loader is in OTP/ROM, you can't erase it or replace it.
You could try adding a jumper to connect BOOT0/VDD this would perhaps allow for connectivity in the case the MCU is getting into the wrong mode via user code. It will not fix Option Byte issues, especially if you disabled SWD/JTAG connectivity, as RDP 2 is non-reversible.