When changing WordPress site url in database from http to https, its important to also make sure that in wp-config.php there is the following code:
define('FORCE_SSL_ADMIN', true); if (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https') {$_SERVER['HTTPS'] = 'on';}
Source: WordPress Developer Resources - Using a Reverse Proxy