If you don't know what the dynamic payment button is? Go to here.
The key is the dynamic payment button will skip the cart attributes when complete the order payment.
So if you have required attributes on cart page, you should disabled the dynamic payment buttons so that guide the customer place an order through standard checkout flow.
How to disable?
Some theme will allow you to config if show dynamic checkout button on product page or cart page, like the pictures show you:
Uncheck 'show dynamic checkout button'.
Now customers will place order through standard checkout flow, and choose payment methods on payment page. Like this:
If you can't find where to disabled on your theme, please contact firstname.lastname@example.org.
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