If you are trying to render with Chaos VRay the first step is ensuring you have a compatible version - each release of Yeti is built against a specific version of VRay, you can check which version was used for the build in the release notes.

Once you have confirmed you are using compatible versions then you will need to check your environment variables. 

The variables VRAY_FOR_MAYAXXXX_PLUGINS, VRAY_FOR_MAYAXXXX_TRANSLATORS_PATH and VRAY_PLUGINS will need to be set as per the rendering extension configuration documentation - these can be set in your System Environment variables or via Maya.env. 

Be sure to replace XXXX with the version of Maya you are using, so for Maya 2024 this would be:

VRAY_FOR_MAYA2024_PLUGINS += C:\Program Files\PeregrineLabs\Yeti-5.0.0_Maya2024\bin VRAY_PLUGINS += C:\Program Files\PeregrineLabs\Yeti-5.0.0_Maya2024\bin
VRAY_FOR_MAYA2024_TRANSLATORS_PATH += C:\Program Files\PeregrineLabs\Yeti-5.0.0_Maya2024\plug-ins

It is also recommended to add Yeti's bin directory to your systems PATH variable:

PATH += C:\Program Files\PeregrineLabs\Yeti-4.2.11_Maya2024\bin

You can confirm these are being passed into your working environment by using the getenv command in Maya, for example:

getenv("VRAY_FOR_MAYA2024_PLUGINS")
getenv("VRAY_FOR_MAYA2024_TRANSLATORS_PATH")
getenv("VRAY_PLUGINS")

The result of each command should reflect the values you've set. 

In the event that Yeti is complaining it isn't able to read/write the intermediate cache files please check that the directory exists and with the right access permissions.