If a member reports they are locked out of your site, but their account is not showing it as a lock out then it is a "browser lock out".
Even though the message may say they are locked out for 24 hours, the time period of lockout is usually around 20 minutes.
The member can wait more than 20 minutes without retrying and they should be able to login.
Alternatively, to allow them access faster, ask them to clear their browser history and cookies, shut down the browser and open the browser again. They should be able to login now.
Or if the user has access to a different browser, they should be able to login immediately.