Errors attempting to sign a git tag

Getting errors when attempting to do a tag ^ sign it, using a form of the command as follows:

$ git tag -u KKKKKKKK -m "Tagging <program> vM.NN" TAG
error: gpg failed to sign the data
error: unable to sign the tag

Where:

1.  "KKKKKKKKK" is the keyid being used to do the signing.
2.  "<program>" is the name of the program in the example commit message for the tag.
3.  "vM.NN" is the version number for the program in the commit message for the tag.
4.  "TAG" at the end is the tag that is being set.

Same thing happened with a different git repository. This is on a system running Debian 9.
I'd had no problem doing the same thing in a different git repository quite recently.


https://stackoverflow.com/questions/41052538/git-error-gpg-failed-to-sign-data

$  export GPG_TTY=$(tty)

Adding that allowed me to do it when logged in directly on the system itself but not when using ssh to log in remotely.