When I was following this tutorial to setup GnuPG for mutt account profiles on my personal laptop, I hit gpg-agent is not available in this session error when I was trying to decrypt my profile. Also, I have to type my password for every time when I try decryption.
This is annoying.
With a little poking around, I found 2 reasons that could affect my setup. First, the gpg-agent.conf under ~/.gnupg. My current setup is:
default-cache-ttl 999999 max-cache-ttl 999999 ignore-cache-for-signing
Obviously I maxed-out the expiration time gpg-agent stores my password in cache (the default-cache-ttl value. It used to be 0).
Secondly, I installed gnupg2 long time ago and I was using gpg-agent for GnuPG 2, the gpg command is actually from GnuPG 1. This confused me a little to figure out. Make sure to use gpg2 command rather than gpg.
If you are encrypting mutt profile too, make sure to use gpg2 everywhere.
Finally, run this at boot time to start an agent daemon.
gpg-agent --daemon --allow-preset-passphrase