Cannot get sudo to work for a user on Ubuntu 22.04.3 LTS

I have added user1 to sudoers group. This confirmed successful as follows:

user1 : user1 sudo

I believe the permissions are set correctly in visudo as follows:

# Allow members of group sudo to execute any command%sudo   ALL=(ALL:ALL) ALL

I have logged in and out. I even rebooted the server. I get the following error when I execute:

sudo ls*entered password*Sorry, user users1 is not allowed to execute '/usr/bin/ls' as root on server1.

I have read countless articles on sudo. I cannot see that I am doing anything wrong. Help appreciated.