Hi,
For almost 2 years I have Lenovo Legion Y520-15IKBM.
I noticed that I have an old version of the system (1803). Windows did not inform me about this.
Trying to upgrade to 1903 (or 1909) the problem occurs:
The Windows support page has a guide on what to do in this case...
bluetooth
device manager
driver issues
installation
lenovolenovovantage
pc issues
realtek
support
system version
tech support
troubleshooting
upgrade
upgrade problems
user guide
version 1903
version 1909
windows 10
windows update