How can I select a different bank account to reconcile?

You can only reconcile one bank account at a time.

If you want to select another bank account to reconcile, you must fully reconcile or abandon the reconciliation you are currently working on first.

Select Bank & Cash > Reconcile a Bank Statement.
If the Reconcile Bank Statement screen is displayed, it means you have a reconciliation that is still in progress.
EITHER
Complete your reconciliation
OR
Click Abandon to cancel the current reconciliation.
Note: Clicking Abandon will erase any items selected and remove the current balances you have filled out.
Once you have either fully reconciled your bank statement, or abandoned your existing reconciliation, you will be able see your Bank Account selection screen. You will now be able to select another bank account to reconcile.

Note: If you have fully reconciled your bank statement in error, you are able to unreconcile it via Bank & Cash > Unreconcile a Bank Statement.