NAV2018 - Error setting up single sign on (Web Client) Set-NavSingleSignOnWithOffice365

Hello,

I have this error setting up single sign on in NAV 2018. It works for the RTC but fails setting up for web client. 

Set-NavSingleSignOnWithOffice365 -NavServerInstance "XXX" -NavWebServerInstanceName "XXX"
-NavUser "XXX" -AuthenticationEmail "XXX@XXX" -NavServerCertificateThumbprint XXX -SkipNavServerConfiguration -SkipWinClientConfiguration

New-Object : Exception calling ".ctor" with "1" argument(s): "Invalid URI: The URI scheme is not valid."
At C:\NAV\Dynamics.110.ES.2467855.DVD\WindowsPowerShellScripts\NAVOffice365Administration\Set-NavSingleSignOnWithOffice
365.ps1:357 char:18
+ ... navWebUri = New-Object -TypeName System.Uri -ArgumentList $NavWebServ ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [New-Object], MethodInvocationException
+ FullyQualifiedErrorId : ConstructorInvokedThrowException,Microsoft.PowerShell.Commands.NewObjectCommand