The server cannot process the image.

I’m trying to upload my site logo on Customize tab. I was reading your FAQ and i added this code in my functions.php file:

add_theme_support( '#header', array(
	'flex-width'    => true,
	'flex-height'    => true,
 
) );

But again im getting this error:

The server cannot process the image. This can happen if the server is busy or does not have enough resources to complete the task. Uploading a smaller image may help. Suggested maximum size is 2560 pixels.

I also increased memory limit in my wp-config.php like this: define('WP_MEMORY_LIMIT', '256M');

But its not working.

Any help would be appreciated.