Logout issue with vouchers

[Karez]

Hello am experiencing problems with vouchers log out.
So when someone using a voucher successfuly logs out say with 30 mins remaining on the voucher, The counter/timer /clock doesnt pause the count-down it jst keeps counting so on loging back say 1 hour later , the voucher period has elapsed and the voucher becomes "used and invalid" .. .
please i need to know if there is a solution to this.

thanxs