I got these messages on my website and could not login as the admin, had to disable all plugins in order re-gain access. Now it works only if EE is disabled. I’ve not included every part of the error message below, but I did send a screen shot of it to Lorenzo.
Warning: session_start(): Cannot send session cookie- headers already sent by(…)
…/plugins/event-espresso-core-reg/core/services/session/SessionStartHandler.php on line 65
The screenshot you sent showed that the headers were already sent by wp-file-manager/file_folder_manager.php, line 1. Usually that’s an indication that that particular file is corrupted. Here’s how to fix:
1) Go to WordPress > Plugins, then deactivate then delete the WP File Manager plugin
2) Activate Event Espresso to check if step 1 fixed the issue
3) Reinstall WP File Manager via the WordPress > Plugins > Add New screen.