Warnings in the AbanteCart error log Warning: Accessing store with non-configured or unknown domain
Warning basically indicates that somebody or something accessed your AbanteCart site with incorrect (not configured) domain/URL. It mainly indicates that your site can be accessible with different domains or subdomains that indicates misconfiguration on your web server.
Common example that will trigger this warning is, then your AbanteCart can be reached by www.xyz.com and xyz.com without automatic redirect of xyz.com to www.xyz.com
In this case, you need to set a correct redirect to www.xyz.com within web server or .htaccess configuration.
Also, this warning lets you know that there is a potential search engines issue. If search engines see your site in different domains, they give you penalty.