It's impossible to access website - authorization prompt appears.
There may be several reasons of this issue. To determine them, the following conditions need to be checked:
1. There should be read + execute permissions for IUSR_ <ftp_user> on the domain index page.
2. Root directory for the domains can be under Parallels Plesk Panel protection.
3. Passwords for system user and IIS user can be out of synchronization.
- Go to %plesk_vhosts%\domain.com\httpdocs directory and check permissions for IUSR_<ftp_user> account.
2. It can be checked using Plesk Control Panel. Go to Plesk, domains, domain.com, Protected URLs.
3. The password for IIS user can be synchronized using the following command:
"%plesk_bin%\websrvmng.exe" --update-anon-password --domain-name=domain.tld
Note: this feature is available starting with Parallels Plesk Panel 7.5.4 and the latest hotfixes.