Cannot open Visual Studio - throw error 'cannot run when setup is in progress'
I had this problem with Visual Studio 2017. There were processes in Task Manager named VSIXAutoUpdate.exe. I watched Task Manager and they were spawning and despawning. A few times, a Visual Studio 2017 process would spawn and despawn.
After VSIX Auto Updater stopped showing up in Task Manager, it had applied all of it's background updates and I was able to launch Visual Studio.
I wouldn't recommend killing these processes in the middle of them installing updates, like other answers to this question suggest. Just wait until they finish by watching Task Manager.
C:Program Files (x86)Microsoft Visual StudioInstaller esourcesappServiceHubServicesMicrosoft.VisualStudio.Setup.ServiceVSIXConfigurationUpdater.exe