The “not equal to” operator <> returns TRUE when the two arguments do not have the same value.
A comparison between BLANK and 0 or between BLANK and an empty string returns FALSE.
Use the == operator to treat BLANK and 0 or empty string as different values.
This operator does not perform any implicit conversion between strings and numbers.
The following are valid expressions using the “not equal to” operator.

Product[Color] <> "Red"
Sales[Quantity] <> 0

See Handling BLANK in DAX for more details about BLANK comparisons.