There is no demo version!!! There's LW Basic which is free & LW Pro which costs US $18.88 You can use either one for as long as you like. There's no dramatic differences between the two. They're almost the same. Pro is almost a donation to keep LW devs in business & continuing to develop. I used the same version of LW Basic for 3 years. I'm now using Pro.

See License requirement (click on link) & see if that's your problem.