Wordpress theme update issue in Temaphp

[hasteL]

Hello, a year ago, I purchased a theme from wmarac? for my website. The theme was working seamlessly, but when I enabled PHP versions above 7.1 from the cPanel, a critical error occurred on my website. I am receiving a warning message like "Learn more about debugging in WordPress." The person from whom I purchased the theme had assured me that the theme would work flawlessly this way, so I had deleted their contact information since there were no issues for a year. The theme is working fine with PHP 7.1 in cPanel but not in other versions. Can you suggest a solution on how to proceed and resolve this issue? I would appreciate your assistance.