Sometimes on my business laptop Windows Subsystem for Linux refuses to start.
This is often caused by antivirus software. Although this happens not very often, this can be fixed by restarting the Lxss service using cmd (with administrator privileges):
sc stop LxssManager
sc start LxssManager
Nevertheless, it is always helpful to read system logs and understand why something went wrong. To explore the issue:
CTLR + R will open the execute shell.
Type in eventvwr.msc
and scroll through events to find out if there are serious issues with other services that hemper WSL.