Data in VLOOKUP formula does not update when data in the range changes.

[SwagBag]

On Sheet 1 I have a List in dropdown box (generated by a range name to a list in Sheet 2).
In Sheet 2 in Column M I have a list of names (that populates the validation list in Sheet 1). In Column N I have their E-Mail address.
Back on Sheet 1 I am using VLOOKup so when somebody choose a name from the drop down, their E-Mail address appears in as cell below.

The formula I'm using is

=VLOOKUP(D35,Sheet2!$M:$N,2,FALSE)

Now this is working perfectly.

However, the E-Mail address for one user has changed so when I update the address in Sheet2, the data in Sheet1 isn't changing. It's keeping the old value/address.

I've tried deleting and re-adding the line but just can't figure out why the change in Sheet2 isn't being reflected in Sheet1 via the formula...

Any ideas clever people?

 

[SwagBag]

Ok, SO I figured out I can do it by changing the data that generates the dropdown (Column M) - but this should be fixed data. As a workaround, I added a whitespace to the value to get it to work but I'd prefer to get the data to update properly..

It seems the the values in column M and N are basically forever connected..