Theme option code not working

Hello,
Do other fields/metaboxes registered with CMB2 work for you? Also, is the CMB2 plugin active?

Hi,
Thank you for reply.
I have included example-functions.php file and it is working normally when register metadata for page, but when i try theme option example code, it is not working.
I also try this code to add example option for Settings > General and it is working fine: https://github.com/CMB2/CMB2-Snippet-Library/blob/master/options-and-settings-pages/add-cmb2-settings-to-other-settings-pages.php

Best regards

Just to be certain, do you have this line as well?

add_action( 'cmb2_admin_init', 'myprefix_register_theme_options_metabox' );

I just added this to my twentyseventeen local theme and hit save, and it created a top-level menu item in the admin. Not sure what may be going on for your case at the present moment.