Delete the WaveVrInput from the Plugins folder, which I think is not compatible with 4.20. Try again. But the best thing you can do is to open the sample project of the new sdk, with what comes by default, without adding the WaveVRInput plugin (only the WaveVr folder and the WVR folder in Thirdparty should be in Plugins, but in the folders where you have installed the engine: For example C: ProgramsFiles / EpicGames / 4.20 / Engine / Source / ThirdParty). With that he must open. Unfortunately, in your project, you will have to access the input commands with the new configuration offered by this new plugin.