Hello! The same thing happened to me today and I fixed it by installing a previous version of Epic Games Launcher, version 18.8.1 specifically. I recommend uninstalling Epic Games Launcher and Epic Online Services and then installing 18.8.1 from here: https://epic-games-launcher.en.softonic.com/versions
During installation it will download the latest update (which caused the issue) but you can decline installing it later by pressing ‘Cancel’.