DAX Using a Measure in formula produces a blank and can't see why

I have cross posted this question with MR. Excel ;

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Hi, i have the following measure formula in DAX power pivot to retrieve the previous unit value, I have attached the workbook with examples of each.

so first to get the previous date ;

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Then ;

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So I thought I should be able to use the first measure inside the second,

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But this just return a blank? Any explanations as to why?