Hello @Testingisfun,
Please try to specify authentication credentials with the proxy host. For example:
testcafe chrome my-tests/**/*.js --proxy username:password@proxy.mycorp.com
If this does not help, please provide us with a link to the problematic page with temporary credentials so that we can see the issue locally. If you do not want to share your web site with other users, you can send a private message to me.