Filter having conditions from multi[ple tables

Hi Jeenz 

The UNION function in DAX doesn't remove duplicates like it does with SQL.  Is that the problem?  If so, change this line as follows

VAR UnionResult = 
DISTINCT(
    UNION(C1,C2,C3,C4)
)

For what it's worth, I wonder if you coule simplify your measure immensely with the following

CALCULATETABLE(
	VALUES(Reseller[Company Name]),
	Vendor[Parent Vendor] <> "Microsoft", -- continue this as necessary
	Reseller[Is Test Reseller] = FALSE(), -- you should have set this as a boolean field, not text
	Subscription[Is Trial] = FALSE(), -- also boolean
	('Calendar'[Date] >= DATE(2020, 6, 1) &&
	'Calendar'[Date] <= DATE(2020, 7, 1))
)

 Hope this helps!