Broken LibreOffice Calc GPG Encryption?

I’m trying to protect a LibreOffice ( on Ubuntu 20.04.1) Calc sheet with GPG encryption.

I have created my GPG keys using:

gpg --full-generate-key

When I come to save the Calc sheet, I selected the Encrypt with GPG key option, then Save, then select my certificate, and click the Encrypt button.
This part seems to work fine

But when I try and open the file again I’m prompted to enter a Password (not Passphrase), and if I provide the GPG passphrase I used to generate the GPG keys Calc tells me The password is incorrect.

Note: Writer has the same issue.

I must be doing something wrong, or is this feature bugged?

Are you able do decrypt your file without LibreOffice as an intermediate level (i.e. using your file manager or on command line)?

Encrypting with LibreOffice doesn’t create a .gpg file, so command line decryption (gpg -d [fileName]) doesn’t work.

Confirm. The .odt (writer) file I created with my GPG cert still unzips from the commandline. The encryption doesn’t happen.