We have checked your system set up and couple things that cause troubles:
1. You are using IIS web server. AbanteCart reported to work under IIS before, but this is not supported by our team.
2. There can be issues with Edge browser as well.
3. This can be the reason as well:
https://support.microsoft.com/en-us/kb/175662All comes down to one issue that session on your server is reset on every web request.
Because of that, login and other session related operations will not be possible
We will keep an eye on this and once Edge is moved from beta state, we can address this if it is still an issue.