I have checked it, and can confirm that all my payment extensions are fully compatible with the aheadWorks Gift Card extension:
Could you please try with only gift card product in cart?
I have checked all the my payment extensions again with a sole «gift card» item in the card, and can confirm they are fully compatible with it:
I have noticed today a bug in aheadWorks Gift Card: aheadWorks Gift Card adds its entry at the end of a totals array, and its «value» is incorrect (always 0).
I affected my 歐付寶 allPay payment extension, and I have updated the 歐付寶 allPay extension today (version 1.1.35).