We’ve recently run into this strange problem on Invoice Ninja (not self-hosting).
In the client portal, after clicking “Credit Card” under the “Pay Now” box, the credit card fields are not displaying. Contact information and billing address is displayed but there is no way to enter a credit card. As a test, I tried to click the “Pay Now” button on the bottom and the following error code reads: The cc_number parameter is required.
We’re using WePay for credit card payments. Our last payment was on July 19th and our clients have not been able to enter payment via credit card since then. I logged into our WePay account and everything seemed fine.
I think if you set it to always the fields for the card details will be shown.
If you remove the gateway I don’t think you’ll be able to add it back.
It’s worth mentioning that WePay no longer supports self host versions of Invoice Ninja, it’s possible since you already have an account it will continue to work.