Pretty hard to say since all you've included is a list of columns...
I'd suggest checking:
1) Data types match for each key field between the two tables. If they do not, they should be made to match
2) Values in B match to a value in A for all of the key fields
Something you could try is to remove the LEFT JOIN and just load the two tables individually. Then, select a value in the Factorized_Units field and see which other fields gray out entirely (all values are excluded) when they shouldn't.