Souretree won't connect to AWS CodeCommit via SSH on MacOS

[vr_driver]

Hi all,

I've spent nearly a day working on this, and I'm now convinced that it isn't possible.

At work, we have moved over from another cloud GIT provider to AWS CodeCommit, and as such, I managed to get SourceTree working on Windows.

However, it is a completely different story on MacOS 11.5.2 (20G95). (Big Sur)

I'm running the latest version of SourceTree 4.1.3 (230) and I've tried everything.

I've loaded the SSH keys from the Windows version, after exporting them to a different format of SSH key that ssh-add would accept. (RSA 4096)

I'm tried connecting to the remote by adding the codecommit URL with and without the @ alpha/numeric username.

I have been able to get it to prompt me with an 'enter password' for the alpha/numeric username, however, it's an ssh key, so it shouldn't be doing this.

When I go to the Security tab in the Settings for my local repository, the "Enable GPG key signing for commits" is not enabled to be selected either.

I started this project initially in my own repository with a bitbucket remote which works perfectly, however, to add a new one and connect to this AWS location just simply won't work on the Mac, when it does on Windows.

I'm really scratching my head on this one.

Has anyone else had this trouble or got it working? Is it me, or is SourceTree not planning on supporting other GIT servers, as it's not in their commercial interest?

Cheers,
Steve

PS. I only post things when I'm really stuck.

[vr_driver]

After trying this out more, we decided to try a 'normal' http connection with a different username. 
I tried doing a 'Refresh' on a pull request so that I could just see the branches available. It showed 'Master' once, then after that it didn't work.
I also tried doing a push request as well. But, it then gives a 403 Error.