How come BLANK() Seems to not be working

I have a DAX formula that seems to not be working. When it falls in the second “if” (see picture). There are Travel Distances that are 0 because it puts them into UNKNOWN when I believe it should fall into the CALCULATE section. Does that make sense?

Travel Distance Range =
IF (RELATED('State Geography'[State Name])="International","International",
IF ('Registration Info'[Travel Distance] = BLANK(),
CALCULATE(VALUES('Travel Bins'[Name]),Filter('Travel Bins', 'Registration Info'[Travel Distance]>= 'Travel Bins'[Min] && 'Registration Info'[Travel Distance] <= 'Travel Bins'[Max])

Looks like you may have to add “Unknown” to your measure. On the second line where you have BLANK, after the () add || ‘Registration Info’ [Travel Distance] = “Unknown”. Let us know if that works. If not we will need to see a copy of your PBIX file.