I've updated the bank details and no transactions are showing for review. Yet the balances are different. How can I rectify?

Do you mean your ending balance is different than the bank balance?

If so, yes that will always be true until all transactions recorded in QB have cleared the bank, which for a checking account in regular use is unusual.

You can create a report of all cleared transactions for all time, and its total should be the same as the bank's.  If not, then fix QB's to reflect the bank's version of those cleared transactions, which presumably are what actually happened.