Cannot add Outlook PST file

I have just the other day set up X1 on a trial basis with the intent of purchasing a subscription. I cannot add my PST file which is contained on my C Drive in an DropBox folder. In trying to link Xi to that PST file, I receive a message "Your current Outlook configuration prevents scanning external PST files. Please load PST files directly into your default Outlook profile."

I have noticed that the X1 Outlook plug-ins are successfully installed. Could someone please translate the meaning of "your default Outlook profile". Thanks.

Bill

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