Symptoms
Login to domain.com via FTP fails for all users. The following error message is displayed:
Cannot log in, home directory inaccessible

Cause
There could be several reasons. This error occurs if:

1. The host name is longer than 15 symbols.

2. The domain resolves to a different IP than the one which has been configured in Plesk.

3. The FTP server configuration is broken.

Resolution
1. To change the host name ,right-click the My Computer icon and choose Properties. Select the Computer Name tab, then click the Change button. Specify the computer name as desired and click OK. When done, restart your computer.

2. Please check if domain.com resolves to the same IP it has been configured for in Plesk. You can use the following command :

nslookup yourdomain.com

The returned IP should be the same as the one configured in Plesk for the domain.

3. If the name of your server is shorter than 15 symbols and the domain resolves to the proper IP, it could mean that something is broken in the FTP configuration.

You should follow the steps below to fix the issue:

a. For versions 8 and 9 only: Repair permissions on the home folders of problem domains. This can be done using the Control Panel:

Plesk , domains, mark problem domain, Click on Check permissions

b. Re-configure the FTP configuration using the Plesk command line tool ftpmng.exe as follows:

Note: The below commands will not affect functioning of your Web (HTTP/HTTPS) sites. However any custom FTP configuration will vanish.

Remove your domain entry from FTP server configuration:
“%plesk_bin%\ftpmng.exe” –remove-vhost –vhost-name=yourdomain.com

Add your domain vhost entry into FTP server configuration and reconfigure it:
“%plesk_bin%\ftpmng.exe” –reconfigure-vhost –vhost-name=yourdomain.com

c. If this issue happens to every domain, you can repair the FTP configuration for all domains using the following commands:

Note: The below commands will not affect functioning of your Web (HTTP/HTTPS) sites. However any custom FTP configuration will vanish.

Remove all domain entries from FTP server configuration:
“%plesk_bin%\ftpmng.exe” –remove-all

Add all domain entries into FTP server configuration and reconfigure them:
“%plesk_bin%\ftpmng.exe” –reconfigure-all
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Reference : http://kb.parallels.com/en/549