Here are a few things to check. Without additional information this is tough to diagnose.
Verify that your session driver is set to Redis in your config/session.php file. If you're using a different session driver, it's possible that this could be causing the issue.
Check that your server time and time zone are set correctly. If the server time is incorrect, it can cause sessions to expire prematurely.
Check that your application is not being served from multiple sub-domains, which can cause cross-site cookie issues, leading to the session expiration.