Hi kennethykw,
It is possible that this is caused by a conflict with another plugin. Can you try disabling all your plugins except Login With Ajax, then create a page with the [login-with-ajax]
shortcode and try to login from that page to see if it works?
If that does not work, that may be an issue with your server so we recommend that you contact your hosting provider or that you create a ticket on the Login With Ajax support (https://wordpress.org/support/plugin/login-with-ajax), as unfortunately the installation, setting or debugging of third party plugins isn’t part of the support we will provide for our theme (Gwangi) and our plugins (Grimlock suite).
Regards,