Hello.

After log in to Webshop, My Account page is displayed. You can check in Webshop and CMS > Settings > My account settings if you have it set up.
I checked but in 8.4 version and I do not have any problems with loging in.

Webshop Sample is set up in SAF installation so you can download Standard ERP for SAF and look inside system how some sample Webhop is set up. I am not able to tell you from your description what is wrong with your data.
With this data login is 006 and pass 006.