If TwistedBrush Pro Studio or any other Pixarra Studio product doesn't start or run correctly in Windows 10, or you are not able to activate the product and you keep seeing the "Invalid Key" error message though you are sure that you have a working key and you have copied and pasted it correctly into the program, then you may have some restrictions on your PC or you may experiencing a Compatibility problem. Here are the things you can do to solve the problem:

1. Run the program as an administrator. This can be accomplished by right-clicking on the program icon and selecting "Properties". Then, in the Compatibility tab check the "Run as an administrator" option.

2. If "Run as an administrator" option doesn't solve your problem, you may have compatibility problems. To solve this ry to run the program in Compatibility mode. In the same Compatibility tab check the "Run this program in compatibility mode" and select Windows 7 from the drop-down menu.

You can also check this FAQ about other common problems with starting TwistedBrush in Windows Vista, Windows 7 or Windows 10 system.