Basic form not working?

Product: PowerShell Universal
Version: 4.3.2

When testing out -buttonvariant on a form I created a blank app using this code I grabbed directly from the docs

    New-UDForm -Content {
    New-UDTextbox -Id 'txtTextField'
    New-UDCheckbox -Id 'chkCheckbox'
} -OnSubmit {
    Show-UDToast -Message $EventData.txtTextField
    Show-UDToast -Message $EventData.chkCheckbox
}  

I get this error message on page load

No errors in the app specific log

I restarted the app and the server hosting it as well