Ok, but …;-)
I tested the installation on 3 different WP Installations, all throw errors, when activation your plugin. I think the problem is your plugin not an interfering one.
Perhaps this warning may help to solve the problem. (I shortened the path)
Warning: ini_set(): A session is active. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 127
Warning: ini_set(): Headers already sent. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 136
Warning: session_name(): Cannot change session name when session is active in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 140
Warning: ini_set(): Headers already sent. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 148
Warning: ini_set(): Headers already sent. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 149
Warning: ini_set(): A session is active. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 150
Warning: ini_set(): A session is active. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 153
Warning: ini_set(): Headers already sent. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 155
Warning: ini_set(): A session is active. You cannot change the session module’s ini settings at this time in /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php on line 157
Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php:127) in /wp-admin/includes/misc.php on line 1282
Warning: Cannot modify header information – headers already sent by (output started at /wp-content/plugins/wp-native-php-sessions/pantheon-sessions.php:127) in /wp-admin/admin-header.php on line 9