This is May from Shopify. Welcome to our Shopify Community!
Check out this list for all payment gateways available in Ecuador that you can integrate with your Shopify store! I personally do not have any experience in using these gateways myself, but I've seen a lot of merchants have 2Checkout as their payment gateway, and it seems to be the most popular third party gateway. After doing some research, I also found that EBANX is something that is worth considering. It is one of the largest payment solutions in Latin America, and I highly recommend checking it out!
If you have any questions about these payment gateways, you can reach out to their support directly from their website. Let me know if this helps!