Hello,
Enable debug mode in WordPress – https://wordpress.org/support/article/debugging-in-wordpress/ to find out what error appears on your site, it will point you in the right direction what needs to be fixed.
Could you, please, create FTP access? We don’t need cPanel, only FTP host, FTP username and FTP pass. If you do not know how to create FTP contact with your hosting provider, they will help you.
Waiting for your reply.
Regards