Payment currency not allowed Craft 3.3.8

Commerce 2 Lite Version

If I change the base currency from default(USD) to NZD or AU in the setting

CP &gt; Commerce &gt; Store Settings &gt; Payment Currencies

and browse to /shop/ or /shop/[otherpages] the website shows error:

Invalid Configuration – yii\base\InvalidConfigException
Payment currency not allowed.
1. in vendor/craftcms/commerce/src/elements/Order.php at line 1580


And if I switch it back to USD it works fine. It also works fine if I am a public register.

I need to use NZD only, if not, I'm open to other work arounds using USD.
Solution from Craft: 


  In your Control Panel, click on Commerce then on the vertical subnav (where you have All Orders, New, Shipped....) you will have Active and Inactive carts, this is what Luke suggested you clear.


Essentially, it looks like existing carts may exist which are still using the old currency. Therefore these must be cleared before changing default currency.