This error message can occur with applications built using the Wacom Ink SDK for Signatures, including sign pro PDF.
It normally indicates one of two root causes:
1. The licence currently being used by the app has expired or is invalid for other reasons, e.g. a non-Wacom pen input device is being used.
2. The app cannot connect to a signature device. Possible reasons for this are:
- The signature device is not connected to the PC - please check Device Manager to see if it is showing there
- For pen display tablets the Wacom Tablet Driver is either not installed or has stopped working
- The signature device is not connected directly to the PC but via a USB hub instead which doesn't have enough power (this mostly affects pen display tablets such as DTUs, not STUs)
Please see also the following FAQs: