This is the second time I've encountered this problem. After the thirty day trial period with XT PRO the program reverts to standard XT and the next time I try to open the program I get the message " the serial number is missing or incorrect. Please re-install DubleCAD XT. " It did it with version 2.0 and now with 3.1.
I've spoken to technical support and told that was impossible. If I was able to open doublecad xt pro version 3.1 at all, then the reversion process should have worked perfectly.
I did open XT pro, the reversion did not work properly.