No idea which table is the "account" table so this is just a guess: change your join to an outer join (all query1 date and query2 dates that match), have date and usage fields from query1 and volume from query2. Another possibility is that the dates don't actually match because you have time values in the date field(s) but have formatted them so that you can't see the time portion. If you think there are identical date values, you can create a test query where you equal join both fields and just return the dates. If no records, they are not the same dates regardless of how they look.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.