Why won’t my venture add to Apple Pay

In which case you need to contact Capital One directly.

Your specific card may not be supported, or you may need to do something through the Capital One app prior to adding it to the Wallet App.

https://www.capitalone.com/help-center/

If you are outside the US when you try to add the card it won't work.

Why not?

What happens when you try?

Do you get an error? If so, what does it say?

Provide details and context about your issue, and someone may be able to advise.