In some cases signing errors occur when using a PKCS #11 provider
key for authentication. If your PKCS #11 provider (for example a
hardware token) has multiple keys, it is possible that not
all the keys can be used for authentication.
Try changing the
Slots value in the PKCS #11 configuration
(see Section PKCS #11 Provider).
When experimenting with the value, saving the settings and restarting
the application, you will see different keys being used for
authentication. Upload the keys one at a time to the remote host computer.
One of the keys may be valid for authentication.