vscode extension can't connect if SSL cert are self signed

[constantinhager]

Create a self singed Root Certificate and a Selfsigned Certificate with the follwing code

$params = @{
    Type              = 'Custom'
    Subject           = 'CN=PSURootCert'
    KeySpec           = 'Signature'
    KeyExportPolicy   = 'Exportable'
    KeyUsage          = 'CertSign'
    KeyUsageProperty  = 'Sign'
    KeyLength         = 2048
    HashAlgorithm     = 'sha256'
    NotAfter          = (Get-Date).AddMonths(120)
    CertStoreLocation = 'Cert:\LocalMachine\My'
}
$cert = New-SelfSignedCertificate @params

$params = @{
    Type              = 'SSLServerAuthentication'
    Subject           = 'CN=updatedashboard.chhome.de'
    DnsName           = 'DEVBOX'
    KeySpec           = 'KeyExchange'
    KeyLength         = 2048
    HashAlgorithm     = 'sha256'
    NotAfter          = (Get-Date).AddMonths(120)
    CertStoreLocation = 'Cert:\LocalMachine\My'
    Signer            = $cert
    TextExtension     = @(
        '2.5.29.37={text}1.3.6.1.5.5.7.3.1'
    )
    Provider          = 'Microsoft RSA SChannel Cryptographic Provider'
}
New-SelfSignedCertificate @params

If I try to use this certificate with the VSCode extension I get the following error messages:

I also checked the forums and did the things described in this post Forum Post.

The Root Certificate is in Machine -> Trusted Root Certification authorities
The normal chertificat is in Machine -> My

Is there any problem with the extension?