This is my experience using xampp virtual server on win10:
The address for the backend is " sitename.com/?s=******* " , where the characters after the "?s=" are the Admin Section name that you specified during the setup routine.
This Admin access location address can be edited in system/config.php.
The "?s=" characters are required; everything after those characters is user specified.
The AbanteCart installer puts the site inside a public_html folder inside an AbanteCart-src-master folder inside the htdocs/sitename folder, which means that the full localhost url to the site will be:
sitename/AbanteCart-src-master/public_html/sitename.com/?s=********* .
You can move the contents of the public_html folder "up" to the htdocs/sitename root.
The site will then run on a typical shorter url: sitename.com/ .
After you move the site files, you'll have to access the backend by navigating to sitename.com/?s=******* ,
then go to System/Settings/Store Details and change the Store URL value to the new root location.
If you can study these name and path concepts to gain an understanding of the basic file structure, you can translate that understanding to your live site hosted on a paid server.
Every host service is different in terms of where they locate site folders in relation to the root folder for your domain.
Step 1 is to learn the file structure required by your host. Does the site run from root, or does it run from public_html? What is the location of public_html? Is it on the root, or is it deeper?
Step 2 is to configure your AbanteCart site file structure to accommodate your host and what you want.
At the end of the day, problems related to being unable to login in to admin on either a localhost or live server are almost always simple differences between the actual location of the site files and the specified location of the site files in config.sys or within the AbanteCart system settings.
Think like this: you put the site files in Folder A, but your settings tell the server to look for the files in Folder B. It is a simple fix. Either relocate the files to Folder B, or change the settings to point the server at Folder A.
Clear cache, and proceed..
Hope this helps.