In a previous version of GiveWP (specifically version 3.17.1), we introduced a feature that hides the Donate Now button when PayPal Donations is selected — and the Smart Buttons are used to complete donations.
When Advanced Credit Card fields are shown as they are in your donation forms (so: the credit card fields show instead of the black Debit/Credit smart button), the Donate Now button is needed to complete a donation, but it is not appearing.
We have this logged as an issue to correct with our development team. While I do not have an ETA yet, I have logged this inquiry to the internal notes of the issue so we can update this post when this bug is corrected.
As a workaround, this works correctly with the Multistep and Two Panel templates, as the bug only occurs on the classic template.
If you’d prefer to use the classic format, the other workaround for now is to change your PayPal Donations settings. To accomplish this, go to Donations → Settings → Payment Gateways → PayPal Donations and change the Payment Field Type to Smart Buttons Only, as shown below. This will add the black button back to the form for Debit and Credit card transactions.
This should just about address it, so I’m marking this one as resolved. Should you have further questions about this, please post them here, or if you have another issue, please create a new post for it.