With a Topaz signature pad configured in KM8 when you issue keys the error Class not registered occurs when attempting to start the Topaz signature pad signing.
KM8: All versions
When KM8 tries to acquire a signature from the Topaz signature pad, it calls the software provided by Topaz for accessing the signature pad hardware.
If the Topaz software is not installed then you will see the error Class not registered.
Download and install the Topaz SigPlus software.
The software may be downloaded from: http://www.sigpluspro.com/sigplus
This download address is included on the papers shipped in your signature pad packaging.
When you install the Topaz software, ensure you choose the correct device type and connection type.