I cannot activate my gift card I bought. I tried used camera and I tried manually but didn’t work.

I have this card and receipt from duane reade/ walgreens store

Ask you money back.

See this Apple article:  If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card

If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - Apple Support

Beware of -> About Gift Card Scams -> About Gift Card Scams - Official Apple Support 

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If you have a valid payment method on file, instead of buying or order an App Store & iTunes gift card, you can Add money to your Apple Account balance anytime, no gift card needed, see -> Apple Gift Card - Apple (UK)

Where to buy a physical Apple gift card: at an Apple Store or an Apple Authorized Reseller in your region 

If you still need help, get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK) 

You will need to contact Apple.

Contact Apple for support and service - Apple Support

Apple gift cards are valid in the country where you bought them.

Shouldn't be this case, contact Apple Support (using the link provided by Kurtosis12).

Regards

Giulio