Unable to connect to the admin page

The email received from Bluehost Support stating the theme is having issues and needs to be fix from the developer. Below is the details of the email.

This is an email to inform you that wp-admin issue is due theme issue. This is the recent log: [22-Jun-2024 15:05:32 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /home3/thefato3/public_html/aitscs/wp-content/themes/corporate-blocks/get-started/getstart.php:103) in /home3/thefato3/public_html/aitscs/wp-includes/pluggable.php on line 1146

Please check with theme support on the issue

The page I need help with: [log in to see the link]