I encountered this error immediately after importing the plugin:
Assets/Plugins/VoxelBusters/CoreLibrary/Runtime/CoreLibrary/Networking/RestClient.cs(3,7): error CS0246: The type or namespace name 'Newtonsoft' could not be found (are you missing a using directive or an assembly reference?)
To resolve it, I made the following change in the RestClient.cs file: I replaced using Newtonsoft.Json; with using Unity.Plastic.Newtonsoft.Json;. This change resolved the errors.
However, when attempting to build for iOS, I encountered another issue with the error message: "Cannot build player when the editor is importing assets or compiling scripts." This occurred while using the latest version of the Essential Kit and Unity 2022.3.12f1.