SCOM 2012 Gateway Failover Script Does not work

Hello,

we try to run a script to Implemet the Gateway-Failover:

$primaryMS = Get-SCOMManagementServer | where {$_.Name –like "x.x.x."}

$failoverMS = Get-SCOMManagementServer | where {$_.Name –like "y.y.y"}

$gatewayMS = Get-SCOMManagementServer | where {$_.Name –like "z.z.z"}

Set-SCOMParentManagementServer -GatewayServer: $gatewayMS -PrimaryServer: $primaryMS

Set-SCOMParentManagementServer -GatewayServer: $gatewayMS -FailoverServer: $failoverMS

we got this error Message :

Set-SCOMParentManagementServer : Cannot validate argument on parameter 'GatewayServer'. The argument is null. Supply a non-null argument and try the
command again.

Any Ideas ?

Thanks

Claus

we got this error Message :