If the problem is related to authentication, remember that resources such as .css or .js can not be accessed until you are authenticated.
That's why the <location>
is used in the web.config to enable access to these files even if you are not authenticated
<location path="carpetaStyle">
<system.web>
<authorization>
<allow users="*" />
</authorization>
</system.web>
</location>
The idea is that you indicate the name of the folder or file that you want to allow access
Setting authorization rules for a particular page or folder in web.config
I would also recommend that you enable the Developer Tools of the browser, which you access with F12, and analyze the "Network" tab to see which files are loaded and if the css that defiens the styles is failing when it resolves the route