An annoying bug can sometimes cause multiple 24h Veteran Memberships to become active at the same time, which makes them all disappear once the time runs out. This happens when you have multiple Veteran Membership rewards already unlocked on your Battle Pass before you purchase the Battle Pass itself.
Upon activating the Battle Pass, all rewards are received at the same time, which under certain conditions can trigger the bug, in particular when the War Server is under a heavy load because of a spike in user connections.
Our devs have created a fix, which will be released with the next update. In the meantime, if you find yourself affected by this bug, please simply contact us and we will compensate you for the days that disappeared.