Hello Dave,
Thanks for reaching out, I’m sorry to hear that you’re unable to Customize your site, that is a puzzling issue.
My first thought is that this error sounds like it may be related to WordPress Multisite. If your network Super-Administrator has not granted individual site Administrators the capability to use the Customizer, that would be the error I would expect to see. At this time, we do not recommend using BoldGrid themes with WordPress Multisite due to multiple compatibility issues we’ve seen.
Other than that possibility, it is possible that your User’s capabilities may have been somehow altered or corrupted. If you are an Administrator, this can be resolved with a WP-CLI command:
wp role reset administrator
If neither of these ideas resolve the issue, can you reply back with your Site Health info? This can be found by visiting yourdomain.com/wp-admin/site-health.php?tab=debug and clicking the “Copy Site Info to Clipboard” button.
Hope this helps for you,
Jesse Owens
Community Manager