Why does the "gpg --gen-key" command give the error "gpg: Key generation canceled" for all user ?

Issue

• Why "gpg --gen-key" command give an error "gpg: cancelled by user" for normal user ?

can't connect to `/home/test/.gnupg/S.gpg-agent': No such file or directory
gpg-agent[24030]: directory `/home/test/.gnupg/private-keys-v1.d' created
gpg-agent[24030]: command get_passphrase failed: Operation cancelled
gpg: cancelled by user
gpg: Key generation canceled.

• Why "gpg --gen-key" command give an error "gpg: problem with the agent: No pinentry" for root user ?

can't connect to `/root/.gnupg/S.gpg-agent': No such file or directory
/usr/bin/pinentry: line 22: xprop: command not found
Please install pinentry-gui
gpg-agent[32309]: can't connect server: ec=4.16383
gpg-agent[32309]: can't connect to the PIN entry module: End of file
gpg-agent[32309]: command get_passphrase failed: No pinentry
gpg: problem with the agent: No pinentry
gpg: Key generation canceled.