Update 7/9/2021: CheckBook and CheckBook Pro 2.6.20 are now available with the fix. Get the update for CheckBook or CheckBook Pro.
To our CheckBook and CheckBook Pro users in Canada and the UK, please accept our apology: We’re patching up an issue that prevents the Account Summary options sheet from appearing and could lead to a crash. Account Summaries will work just fine – it’s only when you try to change their settings or create a new Account Summary that the issue rears its head. 2.6.20 is in testing now so we’ll have you fixed up soon!