Newly added key on Linux Mint 18.1 Serena is unverified. Unable to Login

When I try to login from the command line, I get the following error:

▶ ERROR Sorry, your account is already established with a PGP public key, but this
utility cannot find the corresponding private key on this machine.
This is the fingerprint of the PGP key in your account:

   F50F 4770 8FE0 DFE9 8F32 CE2F D968 92C4 2EDA 2C72

You need to prove you're you. We suggest one of the following:

   - put one of the PGP private keys listed above on this machine and try again
   - reset your account and start fresh: https://keybase.io/#account-reset

When I try to log in from the client, I get just: "Unknown RPC Error"

I think it has something to do with keybase being unable to query the correct keyserver from my machine, based on errors from gpg --refresh-keys output:

gpg: refreshing 2 keys from hkp://keys.gnupg.net
gpg: requesting key <key-name> from hkp server keys.gnupg.net
gpg: requesting key XXXXXXXX from hkp server keys.gnupg.net
gpgkeys: key <Key Identifier> not found on keyserver
gpgkeys: key <Key Identifier> not found on keyserver
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0
gpg: keyserver communications error: key not found
gpg: keyserver communications error: bad public key

Is GPG set up initially in a way that's not conducive to the way keybase checks for login?

Start by reproducing command-line and client login on Linux Mint 18.1 Serena, then compare the reported behavior with the shown gpg --refresh-keys output. Check whether the PGP key lookup and private-key detection fail in the same way; done means the cause is identified and login works or the failure is clearly reported.