Error: Flash Download failed - Target DLL has been cancelled

Hey team,

I am new user to arm Keil platform, and i use keil uvision5. I have 0 errors and 0 warnings. But i can;t load the program or debug the program. The pop-up shows the error that, Error: Flash Download failed  -  Target DLL has been cancelledI do all the possible changes in target utilities, the error remains same.

Note: i can't connect any device through USB. Is this is a reason for the error or not?

kindly let me know the solution with proper guidance or direction notes to solve the error.