Failed to pull GitHub private repo

I know this has been asked before - but I absolutely don't get how to solve it from the responds.
I got the SSH key from

SSH keys

SSH keys

settings, pasted it to my SSH keys on GitHub.

I use the Devcontainer template, with my own repository URL.

I keep getting an error:

envbuilder v1.1.0+a3a6a83 - Build development environments from repositories in a container
#1: 📦 Cloning git@github.com:MyUsername/my-repository.git to /workspaces/my-repository...
#1: 🔑 Using SSH authentication!
#1: 🔑 No SSH key found, falling back to agent!
#1: ❌ Failed to connect to SSH agent: error creating SSH agent: "SSH agent requested but SSH_AUTH_SOCK not-specified"
#1: Parsed Git URL as "ssh://git@github.com/MyUsername/my-repository.git"
Failed to clone repository: clone "git@github.com:MyUsername/my-repository.git": error creating SSH agent: "SSH agent requested but SSH_AUTH_SOCK not-specified"
Falling back to the default image...

envbuilder v1.1.0+a3a6a83 - Build development environments from repositories in a container
#1: 📦 Cloning git@github.com:MyUsername/my-repository.git to /workspaces/my-repository...
#1: 🔑 Using SSH authentication!
#1: 🔑 No SSH key found, falling back to agent!
#1: ❌ Failed to connect to SSH agent: error creating SSH agent: "SSH agent requested but SSH_AUTH_SOCK not-specified"
#1: Parsed Git URL as "ssh://git@github.com/MyUsername/my-repository.git"
Failed to clone repository: clone "git@github.com:MyUsername/my-repository.git": error creating SSH agent: "SSH agent requested but SSH_AUTH_SOCK not-specified"
Falling back to the default image...