Both Scanners (and Scanner for MSBuild is a wrapper over the Scanner CLI, which is ran for React) are making API calls against SQ server, but using different libraries indeed, as the Scanner for MSBuild is written in .NET whereas the Scanner CLI is java.
That being said, they use the same HTTP protocol to achieve that, so i’m really surprise that this work for one and not for the other. Do you pass extra arguments while invoking the Scanner for React directly ?
Is you SQ instance exposed through HTTPS somehow ?