Greetings!
Could anyone tell me why this error happening? and how to solve this problem?
Did you contact Chaos Group’s Customer Support. As a licensed user you have access to direct support from them. They are good at responding quickly and they should be able to get you sorted out.
It’s one month of trial
Well, try contacting them anyway.
FWIW, it might be that the trial doesn’t include that feature. From what little I could read in your blurry screenshot it looks like there’s some error related a license not being found.
Though I used one month trial before but again today i redownloaded and reinstalled it.
I expect Chaos Group already knows you did the one month trial and since that expired you can’t do it again. You would need to purchase a license for Vray.
It looks as if part of vray isn’t installed correctly - reinstall it and see if that helps.