I can't customize gp premium - editor is full empty

So you have an error related to the Custom Checkout Layouts plugin.... if you cannot access the Plugins list, then you will need to delete that plugin from your plugins folder using FTP or from the servers file editor.

I deleted Custom Checkout Layouts plugin, so I can go to dashboard. But Appearance>>Generatepress>>customize is still full empty.

Can you try increasing your PHP Memory limit to 256mb or greater.

I increased it, but prolem not resolved

Can you check with the host that the PHP Memory limit has been increased - setting it in the wp-config will only apply if the Host hasn't capped the memory limit. You should also check what PHP version you're running - for best results you want at least 7.4

My PHP version is 8.0.2

Now I tried to customize generatepress premium on dashboard. Here is xampp\apache\logs\error.log:

[Tue Mar 30 07:25:21.398894 2021] [php:error] [pid 5728:tid 1824] [client 127.0.0.1:63855] PHP Fatal error: Uncaught ValueError: Unknown format specifier """ in C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\customize\\class-wp-customize-themes-section.php:90\nStack trace:\n#0 C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\customize\\class-wp-customize-themes-section.php(90): printf('V\\xC3\\xA1ratlan hiba....', 'https://wordpre...')\n#1 C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\class-wp-customize-section.php(339): WP_Customize_Themes_Section->render_template()\n#2 C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\class-wp-customize-manager.php(4028): WP_Customize_Section->print_template()\n#3 C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\class-wp-hook.php(292): WP_Customize_Manager->render_section_templates('')\n#4 C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\class-wp-hook.php(316): WP_Hook->apply_filters(NULL, Array)\n#5 C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\plugin.php(484): WP_Hook->do_action(Array)\n#6 C:\\xampp\\apps\\wordpress\\htdocs\\wp-admin\\customize.php(281): do_action('customize_contr...')\n#7 {main}\n thrown in C:\\xampp\\apps\\wordpress\\htdocs\\wp-includes\\customize\\class-wp-customize-themes-section.php on line 90, referer: http://127.0.0.1/wordpress/wp-admin/themes.php?page=generate-options

My guess is that you have plugins activated that are not compatible with PHP 8. What happens if you downgrade to PHP 7.4?

I would try to downgrade, but I don't know how to do. I'm using xampp. Can you help me?

Hi there,

XAMPP isn't under our scope of support but to help you out:

Consider using Local (by flywheel). https://localwp.com/

It allows you to create multiple local sites with options to use different PHP versions on site creation as shown here: https://share.getcloudapp.com/4gu2zAde