There is a space to the left of "Lima..."  Your expression also assumes
System ID is numeric.

Using blanks (especially leading blanks!!!) in form and table names,
and not using brackets appropriately. Does your table Lima Caller
Mapping Tables actually have a blank in the table name before the L?
Surely not! The blank in the form name is being interpreted by DLookUp
as the end of the string - it has no idea what Forms!B_W might be, and
the strings "Master" and "Data!MachineID" are just hanging out there
loose. Any time you have blanks or special characters in a name, you
must use brackets to delimit the name.

Try

=Dlookup ("[Support Area]","[Lima Caller Mapping Tables]","[System
ID]=" & [Forms]![Form B_W Master Data]![MachineID])

and consider simplifying your object naming convention.

                 John W. Vinson[MVP]