When you run SliQ Invoicing you will always see the registration window until you have purchased and entered the licence key. However, if you have bought the licence and you get the registration dialogue it is because the registration file has been removed from your PC.
SliQ stores all its data in this folder: My Documents\SliQinvoicing3
If you have moved or deleted this folder and you run SliQ, SliQ will assume it’s the first time you’ve run it on the PC and will recreate the folder. Have you moved or deleted anything? Please check your recycle bin.
If the problem is not resolved try entering your licence key again.
If the problem reoccurs please raise a support ticket and someone will contact you.