Hi,
I'm not able to reproduce the problem with normal HikaShop coupons.
Note that the TaxCloud plugin adds the taxes to the products in the cart before the HikaShop coupons are loaded in the cart. That was already the case before.
However, maybe AWOCoupon uses the same trigger as TaxCloud (onAfterCartProductsLoad) and in that case, if the order of the integration plugins were changed on your website for some reason, It could be possible that the AWO coupons are loaded before the tax are calculated and in that case, the coupon couldn't take into account the taxes and thus you would be left with only the taxes in the cart.
So check that in the Joomla plugins manager.