Permission Denied (publickey) on macOS Sierra with gitlab

[Taylor Matte]

My command-line setup works:

ssh -T git@gitlab.com
Welcome to GitLab, Taylor!

But when I try to pull from SourceTree I get this error:

git -c diff.mnemonicprefix=false -c core.quotepath=false -c credential.helper=sourcetree fetch origin 
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
Permission denied (publickey).
fatal: Could not read from remote repository.

Same error when pushing:

git -c diff.mnemonicprefix=false -c core.quotepath=false -c credential.helper=sourcetree push -v --tags origin refs/heads/master:refs/heads/master 
Pushing to git@gitlab.com:whatever/whatever.git
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
Pushing to git@gitlab.com:whatever/whatever.git
Permission denied (publickey).
fatal: Could not read from remote repository.

 I have checked that the ssh-keys are correct in gitlab and that there are no weird permissions in the repo (which is a shared git repo). Any ideas?

[Manju]

Can you check the agent for loaded keys and see if there is any discrepancy?

This will list all keys. 

ssh-add -l