Why was my Apple Gift Card cancelled?

Are you positive it was Apple who canceled it? They don't say anything about doing that other than if you yourself asked for it to be canceled.

Click on this link about 'Gift apps, music, movies, and more from Apple' --> Gift apps, media, and more from Apple - Apple Support

"Cancel a gift

If you want to cancel a gift, you can contact Apple Support up to two days before scheduled delivery."

If you are sure Apple canceled it then you will have to ask Apple why. The people on this forum are just other users like yourself. This support article has various country telephone numbers for contacting Apple for support and service ➔ Contact Apple Support - Apple Support Scroll down to “Connect with live support”. If your country is not in the list, go to the “Other countries” entry at the end of the list. Not every country has telephone support, and phone numbers may only work when calling from the same country.

For chat, you can try using the Apple Support App —> https://apps.apple.com/app/apple-support/id1130498044

For chat help with a USA Apple Account —>

https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0998&symptom_id=20198

You’ll need to ask Apple. Getsupport.apple.com

This is a user forum, nobody here can help. You'll need to contact Apple Support regarding your purchased gift card.