Plesk reseller traffic not updateing properly.

Try to update the stats for all the domain using given below script were
done without any issue.

/usr/local/psa/admin/sbin/statistics --calculate-all

After completing the above process run the delow scrpit also,

/usr/local/psa/bin/sw-engine-pleskrun
/usr/local/psa/admin/plib/DailyMaintainance/script.php

This may fix the issue. If the above script is not successfull then we
have to check with the plesk upgrade.