Buildx failing to push to private registry

I am trying to create and push a multi-arch image using buildx.

error: failed to solve: failed to push pvt-registry1:4443//test_image_ma:latest: failed to authorize: failed to fetch oauth token: authorization server did not include a token in the response

Digged a bit deeper… This is what i found…

docker buildx build … --push :command is calling POST /token api without Authorization Header.

here is what ~/.docker/config.json is.
“auths”: {
“pvt-registry1:4443”: {
“auth”: “Y2…tZy0t”
“aliases”: {
“builder”: “buildx”

Not sure why that “auth” not getting picked up.

With regular push command, ( docker push…) it is making GET /token with Authorization Header.

Anyone can lend some help to share why it is happening?