Using sudo gives me the error: Sorry, try again

This is what happens when I try :

sudo gedit
[sudo] password for casper:
Sorry, try again.

My username is casper.

I seem to be in the sudo group :

id | grep sudo
uid=1000(casper) gid=1000(casper)
groups=1000(casper),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),116(lpadmin),12 6(sambashare)

Auth log looks like this :

tail /var/log/auth.log
May 16 18:39:18 casper-pc pkexec: pam_unix(polkit-1:session): session opened
for user root by (uid=1000)
May 16 18:39:18 casper-pc pkexec[2426]: casper: Executing command [USER=root]
[TTY=unknown] [CWD=/home/casper] [COMMAND=/usr/lib/update-notifier/package-
system-locked]
May 16 18:42:16 casper-pc pkexec: pam_unix(polkit-1:session): session opened
for user root by (uid=1000)
May 16 18:42:16 casper-pc pkexec[5463]: casper: Executing command [USER=root]
[TTY=unknown] [CWD=/home/casper] [COMMAND=/usr/lib/update-notifier/package-
system-locked]
May 16 18:45:16 casper-pc pkexec: pam_unix(polkit-1:session): session opened
for user root by (uid=1000)
May 16 18:45:16 casper-pc pkexec[7356]: casper: Executing command [USER=root]
[TTY=unknown] [CWD=/home/casper] [COMMAND=/usr/lib/update-notifier/package-
system-locked]
May 16 18:46:55 casper-pc sudo: pam_unix(sudo:auth): authentication failure;
logname= uid=1000 euid=0 tty=/dev/pts/0 ruser=casper rhost= user=casper
May 16 18:47:00 casper-pc sudo: pam_unix(sudo:auth): conversation failed
May 16 18:47:00 casper-pc sudo: pam_unix(sudo:auth): auth could not identify
password for [casper]
May 16 18:47:00 casper-pc sudo: casper : 1 incorrect password attempt ;
TTY=pts/0 ; PWD=/home/casper ; USER=root ; COMMAND=/usr/bin/gedit

Could someone please help me restore sudo? Thank you in advance.

1 Answer

The problem is your sudo package.
You will surely have to remove the sudo package and reinstall it using the synaptic package manager.

Hope this can be helpful for you.

NB: Corrected using OP's comment.