Someone reset your groups on this host, and docker stopped working. Find out why and restore access.

Read the error:

Check which half of Docker still works:

docker version

Compare the socket's owner with your groups:

ls -l /var/run/docker.sock
id

Root can always reach the socket:

sudo docker ps

Add yourself to the group, keeping sudo, and check:

sudo usermod -aG docker learner
id

Now ask the engine about itself: