We've checked the CiviCRM base page (/civicrm), clean URLs enabled, permalinks set to /%postname%/ and CMS integration settings in Civi System Settings are correct.
The "Register" button on the event info page is clicked, rather than a shortcode embedded in a Wordpress page.
Event registration completes but the "Thank You" message configured in the Event settings is not shown (Amounts section and Confirmation page are both disabled as these are free events).
$Fatal Error Details = array:3 [
"message" => "Could not find valid value for id"
"code" => null
"exception" => CRM_Core_Exception {#3586
-errorData: array:1 [
"error_code" => 0
]
#cause: null
-_trace: null
#message: "Could not find valid value for id"
#code: 0
#file: "/var/www/html/wp-content/plugins/civicrm/civicrm/CRM/Utils/Request.php"
#line: 98
trace: {
/var/www/html/wp-content/plugins/civicrm/civicrm/CRM/Utils/Request.php:98 {
CRM_Utils_Request::retrieve($name, $type, $store = null, $abort = false, $default = null, $method = 'REQUEST')
› if (!isset($value) && $abort) {
› throw new CRM_Core_Exception(ts('Could not find valid value for %1', [1 => $name]));
› }
}
/var/www/html/wp-content/plugins/civicrm/civicrm/CRM/Event/StateMachine/Registration.php:27 { …}
/var/www/html/wp-content/plugins/civicrm/civicrm/CRM/Event/Controller/Registration.php:27 { …}
/var/www/html/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php:314 { …}
/var/www/html/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php:69 { …}
/var/www/html/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php:36 { …}
/var/www/html/wp-content/plugins/civicrm/civicrm.php:1199 { …}
/var/www/html/wp-content/plugins/civicrm/includes/civicrm.basepage.php:380 { …}
/var/www/html/wp-includes/class-wp-hook.php:308 { …}
/var/www/html/wp-includes/class-wp-hook.php:332 { …}
/var/www/html/wp-includes/plugin.php:565 { …}
/var/www/html/wp-includes/class-wp.php:797 { …}
/var/www/html/wp-includes/functions.php:1334 { …}
/var/www/html/wp-blog-header.php:16 { …}
/var/www/html/index.php:17 { …}
}
}
]