stm32f103c8t6 cannot connect using stlink after upgrade, how to fix?
I found my Answer to my own question    

Steps to follow to solve the problem  


I have had to pull the BOOT0 pin high during power up to activate the bootloader. Then go to Target menu and Erase chip. 
Put Boot0 to low and the use stm32cubemx and u need to configure the serial wire on stmcube pinout tab. on pinout tab, click SYS and change debug option to serial wire.  
Now everything should work as normal.