This is almost certainly because of invoice caching. That is always the downside of caching – not having live data.
The refresh interval is 30 hours. That can be modified in the spCCG_ARM_PopulateInvoiceBalances procedure. (An advanced option is being added to allow this to be modified in future releases.)
In ARM 3.1.7.x you can refresh the invoices cache by pressing Shift when clicking the Refresh button on the main processes grid.