Gnupg will produce an error such as the one below if ownership and permissions of the directory are not right.
gpg: WARNING: unsafe permissions on homedir '/home/$USER/.gnupg'
This can (and by all mean should) be resolve easily with the following commands:
chown -R $(whoami) ~/.gnupg/ chmod 600 ~/.gnupg/* chmod 700 ~/.gnupg ~/.gnupg/crls.d ~/.gnupg/openpgp-revocs.d ~/.gnupg/private-keys-v1.d
On the last line, add/remove folders according to your environment.