Look inside your server php.ini file

SSH in and type to found your php.ini location: php -i | grep "Loaded Configuration File"

Check:

Lifetime in seconds of cookie or, if 0, until browser is restarted.

session.cookie_lifetime = 0

0 value= Clear session every time you restart the computer or close and open browser.

and

After this number of seconds, stored data will be seen as 'garbage' and

cleaned up by the garbage collection process.

session.gc_maxlifetime = 1440

1440 value Sec = 24 Minutes

both Values need to be at least: 86400

if you change this two values to 86400 your issue must be solved.