Membership Payment 2Checkout Gateway Not Appearing

I have Membership Pro, and I'm trying to use the 2Checkout Gateway, but the gateway isn't loading properly. When a new member goes to register, the 2Checkout button does not show up.

I've checked the page source and it appears the button isn't loading at all.

I've tried deactivating the gateway and reactivating, and that doesn't solve the issue.

I tried activating other gateways, and they all show up. It only seems to be an issue with the 2Checkout gateway.

Also, please note that I can't upgrade to M2 because I need to be able to import 2Checkout recurring members, a feature that is not yet available, so for now I need to work within M1.