Program closes

I purchased emClient for my self about a year ago as I was having issues with my Outlook, but switched computers and now back to Outlook.
But a couple of weeks ago a client was having lots of issues with Thunderbird.
So I installed the free version of emClient, it detected there was Thunderbird installed and offered to import the data, I agreed, but it came up with errors a few seconds later (sorry lost the opportunity to capture that).
I continued and all was working OK.
But when I logged on to the clients computer late last week I see that when the program runs and you get that small dialog before the main program window appears, it then just shuts down, no errors or messages that provide a clue as to why ?
Any ideas ?
Windows 10 which is all up to date.
TIA, Dave

Can you give a screenshot of the small dialog?