Installed Sentinel Snap from official site on a Windows 10 virtual machine. Snap version 6.0.
Checked that I have administrative privileges before install, and asked to install "As an Administrator" to ensure everything runs fine.
After installation, updated SNAP using Tools / Plug-Ins window and selected all available plugins as per next image:
Restarted SNAP and noticed a "update is in progress..." message.
Opened Tools / Plugins menu again, and noticed that the system was not updated. I can see the full available updates on the list available to update.
I had no errors during update process.
Also noticed that when I close SNAP (File / Exit), the SNAP application open again and enters a loop. I close SNAP, and it opens again and no updates are made.