It might help if you posted a copy of this error here.
Title : Title The <title> tags can only contain a call to wp_title(). Use the wp_title filter to modify the output.
Actually, that is not really a critical error. This is because of how the 404 error page is created to have the design style it currently has. I will probably rebuild the error page in the next theme update, but as mentioned, it’s not critical to the functionality of your site and that notice can be ignored until a remake is uploaded.
I should also mention that the themecheck.org is not an official theme check by WordPress, whereas the theme check plugin is what is used by theme authors and WordPress theme reviewers/admins. That error does not show up with this plugin.
Hello, very well thus let us make as if I had say nothing.
I puts the topic solved.
Thank you for your answer