Once a year, SignPro will present you with an error. This is nothing to do with any problems with the application, but rather a natural expiry date on signing certificates. It is nothing to worry about, and is very simple to fix. Just follow these simple instructions.
Go to the directory: C:\Users\[your login name]\AppData\Roaming\Wacom\signpro
Delete all the files inside this directory.
Close SignPro and restart it – it should now prompt you to create a new key.
Once this is done, you should see the error disappear for another year.