Calculate + UseRelationship Syntax with N to N

[mpros]

Hi, 
why this isn't working? Is something related to N-N relationship? Any turnaround?

X(LW) = CALCULATE(sum(table[Quantity]), USERELATIONSHIP(CalendarFull[fnPreviousWorkday],table[_Datex]))

X = CALCULATE(sum(table[Quantity]), USERELATIONSHIP(CalendarFull[Date],table[_Datex])) 

X works aswell with just SUM[Quantity] as active relationship

Calendar Table

[d_rohlfs · Accepted solution]

Hi @mpros,
Your relationship likely doesn't work just because you are using a Many-to-Many relationship. There are a LOT of nuances to using this type of relationship, and this could easily be affecting whether the UseRelationship dax function is allowed to work. 
This post from @amitchandak has a possible solution: Solved: USERELATIONSHIP and many to many - Microsoft Fabric Community

Also, your many-to-many relationship is Limited. This can also affect the useability of UseRelationship. To see what this means, look here:Model relationships in Power BI Desktop - Power BI | Microsoft Learn under "Limited Relationships (it's about half way down).