Credit / Debit Card Option in Payments

We have had quite a few clubs trying to pay affiliation invoices saying the 'pay now' button is greyed out and therefore are unable to pay. 

We understand they have to click the 'credit/debit card' tick box to proceed however this is not very clear they have to do this, the circle is very light and not obvious. 

Is it possible it could be made a little clearer please.