Conflict with WPForo

@berndg17 I already know what the problem is. The filename is always a combination of username and user ID. If you change the avatar, the file has the same name all the time. If you add a new image, my plugin has no information that the avatar has changed.

I suggest you delete the directory:
/wp-content/uploads-webpc/uploads/wpforo/

Also add the following code in the functions.php file in your theme directory:

add_filter( 'webpc_supported_source_directory', function( bool $status, string $directory_name, string $server_path ): bool {
	$excluded_directories = [ 'wpforo' ];
	if ( ! $status || in_array( $directory_name, $excluded_directories ) ) {
		return false;
	}

	return $status;
}, 10, 3 );

This excludes converting images generated by wpForo plugin.