Hello @Saira,
There is a delay between releasing the update and appearing it on the Dashboard. You may wait a few hours, then go WP Dashboard > Updates > press “check updates” link to force check
https://www.8theme.com/documentation/xstore/theme-installation/theme-update/
or you can do the update manually, as described in docs.
https://www.8theme.com/documentation/xstore/plugins/plugins-update/
Regards