Notes

The promo code should appear as applied before placing the order, but I've talked to customers before with the same issue that the code was not appearing as applied and it was successfully applied after they placed the order. So if you already put the promo code in the promo code field it should work just fine.
You can place the order and I can take a look into it to see if the promo code was successfully applied to it.
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Just make sure it meets these requirements, please:
Order subtotal must be at least $15 (before tax, tip, and fees). Offer expires 12/15/2021 at 11:59pm ET. Only valid for use on personal (non-corporate) accounts. Not applicable to catering orders, group orders, or orders containing alcohol. For one-time use only. Cannot be combined with certain other discounts or cash. To redeem, place a qualifying order using the applicable promo link or enter code ENDWALKER at checkout on a qualifying order.
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I can see that the promo code ENDWALKER was successfully applied to you order, I can also see that it covered the delivery fee for $2.99.

Regarding the FINAL FANTASY® XIV promotion, this is the legal text that comes in the promo code:
Limited supply available (expect high demand). FINAL FANTASY® XIV Online “Eat Pizza” emote item codes will be assigned on a first come, first served basis while supplies last. FINAL FANTASY® XIV online pizza emote codes will be sent to eligible recipients via email to the email addresses associated with their Grubhub accounts. Please allow up to two (2) weeks for FINAL FANTASY® XIV Online “Eat Pizza” emote item codes to be sent via email. Valid for delivery orders placed only on the Grubhub platform. Subject to restaurant and delivery availability. Order subtotal must be at least $15 (before tax, tip, and fees). Offer expires 12/15/2021 at 11:59pm ET. Only valid for use on personal (non-corporate) accounts. Not applicable to catering orders, group orders, or orders containing alcohol. For one-time use only. Cannot be combined with certain other discounts or cash. To redeem, place a qualifying order using the applicable promo link or enter code ENDWALKER at checkout on a qualifying order. To redeem the FINAL FANTASY® XIV Online “Eat Pizza” emote item code, you must have or create a North American Square Enix Service account which includes a FINAL FANTASY XIV service account. The item code can be redeemed on the FINAL FANTASY XIV: Mog Station. Item code cannot be redeemed on a trial account. Codes only valid on North American Square Enix accounts. The item will be distributed to a single character of your choice on a selected service account. The item code can only be redeemed once. Once registered, this item code cannot be removed from your service account. Please do not lose this item code, as a replacement code cannot be issued. The transfer or sale of this item code by any means is strictly prohibited. The item code does not expire. Notwithstanding the foregoing, Square Enix reserves the right to establish an expiration date for these item codes by providing advance notice via appropriate channels. FINAL FANTASY® XIV Online “Eat Pizza” emote item codes may be subject to additional restrictions. Offer and participation are subject to the Grubhub Terms of Use. Grubhub reserves the right to cancel, suspend and/or modify any aspect of or the entirety of this offer, for any reason at any time, with or without notice, including, without limitation, if any fraud or technical failure impairs the integrity or proper functioning of the offer.
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I know this has been frustrating for you and for the inconvenience this may cause you. Rest assured, I´m going to do all I can to resolve this for you. Unfortunately, at the moment we won't be able to make any adjustments to the account but I do see here that our specialized team is working on this so we can offer you the best resolution possible. This type of investigations are done internally on our end, but if there's anything we need to reach out to you for, be assured we will contact you.