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 Managing Key Providers).

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.