There can sometimes be differences in the sum of transaction values versus the totals held in the nominal account records. In the first instance:
Establish if the problem is with Transactions, Records - or both - by comparing the TB reports with extracts of the Transaction Enquiry screen.
Check to see when, or if, the Trial Balance (TB) was last correct.
Then, raise a new case online, referencing this article and providing any findings from the above checks.