I'm not finding anything about this in docs. This sandbox account works ok when the user is in USA but when I try to develop from Argentina i dont even see Paypal buttons cause isEligible() js function returns false. Is it related to my country? Being a dev environment is there any way to stop this validation for a while?
I log in the sandbox account and enter our E-Commerce site, paypal user is taken from my sandbox user that's already logged-in in the browser.
What I am doing is exactly what's explained here: https://developer.paypal.com/docs/checkout/integration-features/standalone-buttons/
It works perfectly from United States but from Argentina IsEligible() always return false. I'm using the same Paypal Sandbox account.
It's unusual to be using standalone buttons, a simpler solution would be to just integrate Standard payments with smart buttons. There's also an interactive demo here where you can try everything out.
We can't comment on your specific attempt to use standalone buttons unless you update your question with a full HTML example of what is being done, including the line that loads the SDK script.
If your goal is to test what buyers from other countries will see, in sandbox mode you can add the query string parameter buyer-country=US or similar, as documented here. Do not use this parameter in live mode (with a live client-id) as it will not load.