An error occurred while trying to export OpenPGP certificates. Server indicated a failure gpg: keyserver send failed: Server indicated a failure -snip-
Try changing the OpenPGP keyserver. If you are using Windows OS and Kleopatra as in the tutorial above, go to Settings -> Configure Kleopatra ... In the OpenPGP Keyserver column (default: hkps: //hkps.pool.sks-keyservers.net), enter the keyserver that is still active/accessible, https://pgp.mit.edu;http://keyserver.ubuntu.com/; or other servers; then click OK.