Add and apply SPOTheme to modernsites

I get the error screenshot below when adding and applying this SPOTheme.

It adds the theme but fails to apply it throwing up exception below 

function HashToDictionary {
   Param ([Hashtable]$ht)
   $dictionary = New-Object "System.Collections.Generic.Dictionary``2[System.String,System.String]"
   foreach ($entry in $ht.GetEnumerator()) {
     $dictionary.Add($entry.Name, $entry.Value)
   }
   return $dictionary
}

$themepallette = HashToDictionary(
@{
"themePrimary" = "#4ea3e9";"themeLighterAlt" = "#f6fafe";"themeLighter" = "#edf6fd";"themeLight" = "#dbecfa";"themeTertiary" = "#b4d8f5";"themeSecondary" = "#5eabea";"themeDarkAlt" = "#3194e5";"themeDark" = "#1974bf";"themeDarker" = "#135b96";"neutralLighterAlt" = "#f8f8f8";"neutralLighter" = "#f4f4f4";"neutralLight" = "#eaeaea";"neutralQuaternaryAlt" = "#dadada";"neutralQuaternary" = "#d0d0d0";"neutralTertiaryAlt" = "#c8c8c8";"neutralTertiary" = "#b5b5b5";"neutralSecondary" = "#868686";"neutralPrimaryAlt" = "#6e6e6e";"neutralPrimary" = "#252525";"neutralDark" = "#565656";"black" = "#3e3e3e";"white" = "#ffffff";"primaryBackground" = "#ffffff";"primaryText" = "#252525";"bodyBackground" = "#ffffff";"bodyText" = "#252525";"disabledBackground" = "#f4f4f4";"disabledText" = "#c8c8c8";
}

)
Add-SPOTheme -Name "New Company Theme" -Palette $themepallette -IsInverted $false -Overwrite

Set-HideDefaultThemes $true

thanks