Docker daemon not running

I have installed Docker Desktop on my Mac Book Pro running macOS Big Sur version 11.4.
I am desperately trying to pull some code from GitHub as I am attending a school teaching image reconstruction for the main imaging modalities.
The school instructors have suggested several commands but nothing works for me because the Docker daemon seems to be not running. I keep seeing the following error message:

“Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?”

I have tried restarting my Mac but Docker daemon seems to be unaffected.

I would appreciate some help to solve this problem.
Thank you in advance.