Hi,
2. Thanks ! If you didn't post yet a review for HikaShop on the JED, it would be very appreciated. Every good review helps us.
extensions.joomla.org/extension/hikashop/
1. Based on how your template is built, it's possible there is still some of its CSS loaded on the page, even when using the default template of Joomla.
It could also be another extension's CSS, like a module or a plugin, messing with HikaShop's.
Finally, I don't have the issue on my end with the default template of Joomla, and no one else reported such an issue so far.
So it's highly likely to be something specific to your website.
So again, we'll need you to provide the URL of the page of an order, with the username and password to be able to access the page so that we can look at the CSS/HTML there. Otherwise, we can't check what's wrong.
You can provide the access via our contact form:
www.hikashop.com/support/contact-us.html