Too few arguments were passed to AND function. the minimum argument count for the function is 2

Hi butterscotch 

Is this what you meant?

Completion = 
IF(
	AND(
		VALUES(Master[Start Date].[Date]) <= VALUES(Master[Jan-24]),
		VALUES(Master[End Date].[Date]) >= VALUES(Master[Jan-24])
	), 
	TRUE,
	FALSE
)

When using AND(), a comma is used to separate the 2 clauses instead of &&.  It could also be written as:

Completion = 
IF(
	VALUES(Master[Start Date].[Date]) <= VALUES(Master[Jan-24])
		&& VALUES(Master[End Date].[Date]) >= VALUES(Master[Jan-24]),
	TRUE,
	FALSE
)

(I didn't try to fix anything else.)

Hi butterscotch 

Adding to gmsamborn 
Use simple && in DAX

Completion = 
IF(
		VALUES(Master[Start Date].[Date]) <= VALUES(Master[Jan-24]) &&
		VALUES(Master[End Date].[Date]) >= VALUES(Master[Jan-24]), 
	TRUE,
	FALSE
)