How to solve it?

You have provided absolutely no information about the Vegas Pro version and build that you are using, your computer's specs, the Windows version or the media that you are using. Please refer to:

https://www.vegascreativesoftware.info/us/forum/important-information-required-to-help-you--110457/

... and provide the requested information so that those on the forum will be given a chance to help you.

You should also use the forum's search function using the keyword 0x80131501 as you will find quite a few threads about this error code which may be able to assist you.