Try to deactivate and activate the theme using your purchase code and then IMPORTANT: go to Dashboard > Updates > click CHeck again link https://prnt.sc/yygl09
You may try to update the theme after that and you should not face any issues.
And if still you will not able to update it, then please share your site WP Admin URL and Credentials in a private content area of this topic, so that I’ll check and further help you out.
Regards 8Themes Team.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.