How do i resend a gift voucher to another email address?

Hi there, Plantpot41,

Thanks for visiting the Apple Support Communities. We understand that you recently sent a gift to someone and they were unable to receive the gift and/or open it. We're happy to help!

The following steps from Send a gift from the App Store, iTunes Store, Apple Books, and more - Apple Support walk through resending a gift, including what to do if you need to update/change the email address:

"Resend a gift

When you send someone a gift, they receive an email notification. In the email, they can tap or click Redeem to redeem the gift. The item will open and start to download to their device or computer. Then you'll get an email with a line item that says "App Store & iTunes Gift for [email address]."

If you send a gift and the recipient doesn't receive an email, resend the gift.

Resend a gift from your iPhone, iPad, or iPod touch

1. Open the Settings app.
2. Tap your name, then tap iTunes & App Store.
3. Tap your Apple ID at the top of the screen, then tap View Apple ID. You might be asked to sign in with your Apple ID.
4. Tap Gifts. If you don’t see Gifts, then you haven’t purchased any gifts with this Apple ID recently.
5. Tap the gift that you want to resend.
6. Tap Resend Gift. If you don't see Resend Gift, it has already been redeemed.
7. Before you resend, make sure that the recipient's email is spelled correctly. If you need to edit or change the recipient's email address, tap their email address on the Gift detail screen.

Resend a gift from your computer

1. Open the Music app or Apple Books. Or if you're on a PC, open iTunes.
2. From the menu bar at the top of the screen, choose Account > View My Account. (In Apple Books, choose Store > View My Apple ID.) You might be asked to sign in with your Apple ID.
3. On the Account Information page, scroll to the Purchase History section and click Manage Gifts. 
4. If you don’t see Manage Gifts, you haven’t purchased any App Store & iTunes Gifts with this Apple ID recently.
5. Click View next to the gift that you want to resend.
6. Click Resend Gift. Before you resend, make sure that the recipient's email is spelled correctly. To edit the recipient's email address, change the address in the box under Recipient."

If you still need help after that, please contact Apple Support directly: Get Support.

Have a wonderful day!