Docker login error only with AWS - x509: certificate signed by unknown authority

I am running Docker on an Ubuntu distro in WSL (Windows linux subsystem). I have the wsl-vpnkit installed and working … and AWS CLI,
My network settings work with a remote repository elsewhere in the company. I can use docker login from the WSL Ubuntu shell and then docker pull to get an image.
So … I then wish to push an image from my local Docker client repo up to Amazon (AWS) ECR registry. I can use ‘aws get-login-password’ to get an authorization token …
So so far all good.
BUT … when I try to login to my AWS region with ‘docker login’ I get this error
Error response from daemon: Get “”: x509: certificate signed by unknown authority

My and above are correctly substituted with the real values of course.
And my local AWS configuration (AWS Access Key ID amd AWS Secret Access Key) are all good (otherwise I couldn’t bet my auth token above)
So WHY do I still get this error.
I have checked my ca-certificates in Ubuntu … all good including the corporate certificate.
Things only go wrong when I use docker commands … and of course talk to the AWS registry
Can anyone assist?