Why are coupon codes not working after theme update?

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Hi there!

I updated my client's theme last week as part of a website refresh as they had not updated it in quite a while. They have since had a few customers indicate that the coupon code they're trying to use is not reflecting the discount at checkout. Wondering if the theme update would have messed up anything with set discount/coupon codes or if it's just a coincidence with timing of the update. They typically haven't had anyone have coupon code issues in the past. Thanks!

Theme is Blockshop in case it makes any difference!