Either the GpgME library itself is too old, or the GpgME++ library was compiled against an older GpgME that did not support connecting to gpg-agent.
Pode que a biblioteca GpgME mesma sexa vella de máis ou que a biblioteca GpgME++ se compilase cunha GpgME que non aceptaba a conexión cun gpg- agent. @ info