When running the PST Enterprise Client, you see that the PSTEnterpriseClient.exe process starts up but no PST files are discovered and no processing takes place. Examining the PST Enterprise Client log you can see that the initialization of MAPI fails:
30 14:13:56 FileIterator::IterateFiles MAPIInitialize failed 0x80004005
30 14:13:56 There has been a problem connecting to your messaging system, error 0x80004005
Outlook is not installed on the machine where you are running the PST Enterprise Client. Looking at the start of the client log, you can confirm this:
30 14:13:54 Outlook version not Installed
Outlook is a pre-requisite for the PST Enterprise Client (https://campus.barracuda.com/product/pstenterprise/article/PST/SystemRequirements/).
You must install a support version of Outlook on the machine where you are running the PST Enterprise Client.