One can configure Windows firewall to log VPN connections but that is not a default. Check Control Panel > Windows Firewall > [Advanced tab], the default location is C:\WINDOWS\pfirewall.log for the log file. Specific applications used may have preserved log data.

/var/log/openvpnas.node.log (in case of a failover setup) In the event that you are having problems with starting the Access Server or certain portions of it, for example the web services, then it may be useful to stop the Access Server service, move the log file aside, then start the Access Server service, and stop it again immediately. VPN Logging Policies Reveal Only 3 out of 101 Providers Furthermore, Astrill VPN also logs last 20 connection records such as connection time, connection duration, country, device type, and Astrill client application version number. However, they claim that this information is only used by the customer support team and automatically removed in case of no activity is performed in the past 30 days . What Information do VPN's Really Log? | VPN University

KeepSolid VPN Unlimited® – Best No-log VPN | Zero-log VPN

Seven 'no log' VPN providers accused of leaking – yup, you Jul 17, 2020

KeepSolid VPN Unlimited® – Best No-log VPN | Zero-log VPN

Feb 28, 2015 VPN connection: What does it mean and why do you need one?