What is a 'Steam client' issue and how can I resolve it if it's causing fatal errors?

A Steam client issue could involve a corrupted Steam installation or outdated version. Try restarting the Steam client. If that doesn't work, attempt a Steam client repair by going to Steam > Settings > Downloads > Verify Steam Files. As a more drastic measure, uninstalling and reinstalling the Steam client can resolve persistent issues. Ensure your Steam client is up to date before launching CS:GO.