If you are experiencing an error similar to below when publishing regular WordPress pages and posts:
Warning: Cannot modify header information – headers already sent by (output started at … /public_html/wp-content/plugins/optimizeMember/includes/classes/admin-notices.inc.php:87) in … /public_html/wp-includes/pluggable.php on line 1207
This issue has been found to be caused by not having selected a Membership Options page within the OptimizeMember settings. These can be found within OptimizeMember > General Options > Membership Options
Please choose a page for your membership options page (this can be any page for now – we recommend a sales page or login page) and this error will stop.