Problems adding basic time intelligence to my cube (I'm new at this)

I'm using SSAS 2016. I'm not at all familiar with SSAS but my boss has asked me to add the ability to select a running 12 months for his calculations.

I thought this would be easy using the wizard and adding time intelligence. I selected all the measures in the one fact and just the rolling 12 months option.

When I open the cube in browse, select one measure and then the Twelve Months To Date option under the Date dimension, it gives me an error that A set has been encountered that cannot contain calculated members. There aren't any other parts to the error message unlike other examples of that I've found on-line.

Thing is, none of the measures are calculated except in the source view for the Fact table. Just in case that somehow had an impact, I edited the Scope to remove those 2.

Under calculations in my cube definition, the Twelve Months to Date calculation appears in 3 parts. There's a scope statement:

Scope(
       {
         [Measures].[Transaction Count],
         [Measures].[Transaction Value],
         [Measures].[Interchange Cost],
         [Measures].[Transaction Cost],
         [Measures].[Vision Interchange Cost]
       }
)

A calculation:

/*Twelve Months to Date*/
  ( 
[Dim Date].[Calendar Year Quarter Dim Date Calculations].[Twelve Months to Date],
    [Dim Date].[Month Year].[Month Year].Members,
[Dim Date].[ID].Members 
  ) 

  =

  Aggregate(
             { [Dim Date].[Calendar Year Quarter Dim Date Calculations].[Current Dim Date] } 
             *
             {
               ParallelPeriod(
                               [Dim Date].[Calendar Year Quarter].[Month Year],
                               11,
                               [Dim Date].[Calendar Year Quarter].CurrentMember
               ) : [Dim Date].[Calendar Year Quarter].CurrentMember
             }
  )

And an End Scope.

Hopefully this is an easy fix?

Nick Ryan MIS Programmer Analyst, ANZ Bank