you need to check the theme contains the ispconfig version number. I don't believe the filename and format as changed since this: https://www.howtoforge.com/communit...ged-in-a-theme-3-0-4-3-0-5.61935/#post-297899 the themes here were created before this latest release though, i'm not aware of anything that would break in them, but it's possible they're not 100 percent compatible. once you select the new theme from within the ispconfig control panel, you also need to log out completely and then re-login before the theme change will take effect.
any links to rar files in this thread point to a site that no longer exists. only the download links for zip files work, and only a couple of the themes were saved and made available again as zip files.
instructions are in the opening post. the theme folder also needs to contain a file called 'ispconfig_version' which contains the ispconfig version number the theme is designed for, eg '3.1.3', or '3.2.4' the themes in this thread were all created for ispconfig 3.1.* there's no guarantee they'll work on 3.2.* without changes.