Cannot reset VNC password for KVM VPS from WHMCS interface: Unknown error. Contact support

Symptoms 

Cannot reset VNC password for KVM VPS from WHMCS interface:

SVM_ERROR: Unknown error. Contact support.

Cause

This is a solusvmpro module bug #SVM-1645. It will be fixed in future module releases

Resolution

1. Connect to the server with WHMCS installed via SSH or FTP
2. Create a backup file of modules/servers/solusvmpro/solusvmpro.php file

    # cd <WHMCS_roor_directory>

   # cp -a modules/servers/solusvmpro/solusvmpro.php{,.orig}

3. Open solusvmpro.php file with the text editor, find the line with 'vserver-vncpassword' API method call and replace it with 'vserver-vncpass'. If everything changed correctly, diff command should show the following output:
   

   # diff ./modules/servers/solusvmpro/solusvmpro.php ./modules/servers/solusvmpro/solusvmpro.php.orig
   1038c1038
   < $solusvm->apiCall( 'vserver-vncpass', $callArray );
   ---
   > $solusvm->apiCall( 'vserver-vncpassword', $callArray );