When trying to create a key with gpg –gen-key, I was getting the error:
gpg: problem with the agent: No pinentry
To solve this, first check if pinentry is installed. On Debian systems, use:
apt-get install pinentry
or on Redhat/Centos, use:
yum install pinentry
If you still get the error and you’re running gpg from the command line, the problem is that pinentry is set up to run in a GUI by default. You need to tell GPG to use the “curses” version of pinentry that can be run in a terminal. To do this, edit the GPG config file:
vi /etc/gnupg/gpg-agent.conf
Add or change the line with pinentry-program so that it looks like this:
pinentry-program /usr/bin/pinentry-curses
That’s it! Let me know in the comments if this works for you.
Annoyances and How-Tos 
Thanks dude woks! in openSUSE 13.1 just reload the terminal and its all.
Worked, thank you (had to adapt it a bit for ubuntu)
Worked with centos 7.6, thx! Should also issue the reload command gpg-connect-agent reloadagent /bye
Didn’t work for me.
# gpg –cipher-algo AES256 -c password
gpg: problem with the agent: No pinentry
gpg: error creating passphrase: Operation cancelled
gpg: symmetric encryption of `password’ failed: Operation cancelled
try
gpgconf –kill gpg-agent
echo ‘pinentry-program /usr/bin/pinentry-curses’ > ~/.gnupg/gpg-agent.conf
gpg-agent –daemon
echo test | gpg –clear-sign
This solved a very confounding problem I was having – thanks for posting!
For reference, maybe this will help others:
If running macOS and using MacPorts version of Pass,
you can find the gpg-agent.conf at ~/.gnupg/gpg-agent.conf
and the referenced pinentry-curses location should be in /opt/local/bin/
so enter the line below into gpg-agent.conf:
pinentry-program /opt/local/bin/pinentry-curses