Attempting to upload a file in EE3 file manager triggers an error that says 'This form has expired. Please refresh and try again'. I have tried some config solutions that seem to have worked from EE2 version users such as disabling secure form protection:
$config['disable_csrf_protection'] = "y";
Also tried including the following as another user suggested here:
$config['cookie_domain'] = "";
$config['cookie_path'] = "";
$config['cookie_prefix'] = "";
$config['admin_session_type'] = "s";
$config['user_session_type'] = "c";
$config['require_ip_for_login'] = "n";
$config['require_ip_for_posting'] = "n";
$config['secure_forms'] = "n";
This did remove the error message, however now the upload page merely refreshes when you try to submit the upload. The upload does not complete and is not confirmed.
I've not seen many people have this issue when using File Manager, it seems to be mainly a login issue.