Notice: Use of undefined constant OP_SN

If you see a message like this after installing OptimizePress:

Notice: Use of undefined constant OP_SN - assumed 'OP_SN' in ... /wp-content/plugins/optimizePressPlugin/lib/framework.php on line 494

Notice: Use of undefined constant OP_SN - assumed 'OP_SN' in ... /wp-content/plugins/optimizePressPlugin/lib/framework.php on line 495

How to fix

Normally in cases like this is caused by having debug turned on in WordPress. As this is a php notice, it is not effecting any OptimizePress functions, however the reason it shows at the top of your site may be due to havnig wp-debug turned on.

This would be in your wp-config.php file.

See here for how to turn this off: https://codex.wordpress.org/WP_DEBUG

Basically look for this: define( 'WP_DEBUG', true ); 

and CHANGE it to this: define( 'WP_DEBUG', false );