Tente o seguinte: https://www.enigmail.net/support/gnupg2_issues.php
No meu caso, preciso instalar uma versão gráfica do pinentry (pacote pinentry-qt4).
"Resolvendo problemas com o GnuPG 2.xe o gpg-agent
Nota O GnuPG 2.x requer um "agente" para lidar com senhas. Por padrão, isso é feito pelo gpg-agent, mas existem outras ferramentas que implementam um subconjunto de sua funcionalidade. Estas instruções são apenas para gpg-agent. Se você usa um agente como o gnome-keyring, o seahorse-agent ou o KDE Wallet Manager, essas instruções não se aplicam. Problema mais comum
Sintomas
O problema mais comum é que o gpg-agent (uma parte do GnuPG) não pode iniciar o pinentry (a ferramenta usada para consultar sua senha). O Enigmail exibia mensagens como:
when reading messages:
Error - no matching private/secret key found to decrypt message; click on 'Details' button for more information
when sending messages:
- Send operation aborted. Error - encryption command failed
- Send operation aborted. Key 0x....... not found or not valid. The (sub-)key might have expired
Como analisar
Try sending a signed and unencrypted message to yourself.
Check the output in the Enimgail log: go to menu Enigmail > Debugging Options > View Log.
Search for the following text: parseErrorOutput: status message. You will probably find this message several times. Check what follows below.
If the message says something like "no pinentry", "problem with the agent", "Invalid IPC response" or "problem with gpg-agent", then there is something wrong with your gpg-agent and/or pinentry setup.
Como corrigi-lo
Execute the following script from a terminal to find out if a graphical version of pinentry is used:
pinentry <<EOT
SETDESC Hello World
CONFIRM
EOT
You should get a graphical window with a confirmation message "Hello World". If a "window" is opened within your terminal window then pinentry is text-based, which does not work with Enigmail. To fix this, ensure that a graphical version of pinentry is installed. On Linux/Unix systems, these would typically be pinentry-qt/pinentry-qt4 or pinentry-gtk/pinentry-gtk2, and on Mac OS X pinentry-mac. Rename the existing pinentry file to "pinentry-text" or similar, and create a symlink from pinentry-qt, pinentry-qt4, pinentry-gtk, pinentry-gtk2 or pinentry-mac to pinentry. Then restart your PC.
If the above does not help, check the contents of $HOME/.gnupg/gpg-agent.conf. Make sure that there is a configuration entry pinentry-program containing the full path to a graphical version of pinentry as above. E.g.:
pinentry-program /usr/local/bin/pinentry-gtk
Then save the file and restart your PC.
If you still can't access your key, then execute the following script from a terminal:
gpg-connect-agent <<EOT
GETINFO version
EOT
The output should be something like the text below, where 2.0.26 represents the agent version number. The version number should match your gpg version number:
D 2.0.26
OK
If you get an error message like "ERR 280 not implemented" then you don't use gpg-agent, but one of the alternatives like gnome-keyring. We recommend you switch to gpg-agent by disabling your current agent. See e.g. askubuntu for how to disable gnome-keyring or how to disable KDE wallet.
If you get a useful result from above, then execute the following script from a terminal:
gpg-connect-agent <<EOT
GET_CONFIRMATION Hello
EOT
Pinentry should now open as a graphical window (just like above), with the difference to the step above that this instance of pinentry was launched from gpg-agent. If this is successful, then GnuPG 2 should work correctly in Enigmail.
If gpg-agent still cannot launch pinentry from Enigmail, then you need to start debugging gpg-agent. Execute the following commands from a terminal:
killall gpg-agent
gpg-agent --debug-level expert --use-standard-socket --daemon /bin/sh
This will start gpg-agent from the command line, open a new shell and print the debug output to that shell. If the command succeeded, you will see somehting like:
gpg-agent[76979]: gpg-agent 2.0.26 started
Leave the terminal window untouched, start Thunderbird and try to use Enigmail. As you'll try to access gpg-agent, you will see the output in your terminal window. If gpg-agent cannot start pinentry successfully, you will see something like this:
gpg-agent[76993]: starting a new PIN Entry
gpg-agent[76993]: chan_19 <- ERR 67109133 can't exec `/usr/bin/pinentry': No such file or directory
gpg-agent[76993]: chan_19 -> BYE
gpg-agent[76993]: can't connect to the PIN entry module: IPC connect call failed
gpg-agent[76993]: command get_passphrase failed: No pinentry
Press Ctrl+D in the terminal to end the debugging session. The bold line should tell you the reason for the error (in the example above, pinentry cannot be found). Try to fix the error and repeat the test."
pinentry-gtk2no Ubuntu com Unity