Hello, Arturs
Please make sure you've downloaded the client from our portal (http://l2e-global.com/reg ), and also make sure that you haven't install any third-party software.
After this please follow the next steps:
- disable your antivirus and/or brandmauer/firewall
- make a full check by using updater “L2e-global.exe” in the Lineage 2 root folder
Jus PM me if it won't help