The plugin requires the OpenVR library to work. It used to be provided by Unreal for the SteamVR plugin, but since that has been removed in recent versions, you would have to either backport it, or provide it yourself instead from GitHub - ValveSoftware/openvr: OpenVR SDK.
Note that the plugin will still not work out of the box with newer UE5 versions. The SceneView API has some changes that need to be addressed, and the material based passthrough would need a lot of work to function with the upgraded material systems (or disabled).
Unless you absolutely need support for accessing and modifying the camera images, I’d suggest using the OpenXR API layer instead of the plugin.