Last week, Microsoft announced that it had fixed a number of issues that were causing the upgrade path to the May 2019 Update to be blocked for many users, though some were left unresolved. It seems, however, that a new block has shown up for some owners of the Surface Book 2.
According to the release information page, Microsoft has discovered an issue on Surface Book 2 variants with discrete Nvidia GPUs where the graphics card disappears from the Device Manager after installing the Windows 10 May 2019 Update. This may also make games and apps that rely on heavy graphics processing crash.
Because of this problem, Surface Book 2 units with Nvidia dGPUs have been put on a compatibility hold for the latest Windows 10 feature update. Variants without these Nvidia cards can still update. If you already installed the May 2019 Update, you can try to mitigate the issue by clicking the "Scan for hardware changes" button in the Device Manager.
Microsoft says it will issue a fix for the issue in a forthcoming update, at which point you should be able to get the May 2019 Update again.