I integrate square payment on my wordpress website through WP EASY PAY, the only problem is that it won’t accept any credit card or debit card. Do you guys have any other work around ? I really need it right now, I might lose a job.
Is the Square account that you’re using fully enabled to accept credit cards? 
Yes it is. How Can I enable sandbox mode, btw?
If the WP EASY PAY built a way to test in sandbox then they should have provided some instructions on how to test in Sandbox. All API functions are managed by WP EASY PAY.
Do you have any suggestions on how I can integrate Square Payment into my Wordpress Site?
Since you have a WordPress site, the WooCommerce, WP EasyCart, or WordPress.com integrations with Square would be a great fit.
To learn more about each integration, please visit the WooCommerce, WP EasyCart, or Wordpress.com sites. You can also visit our Seller Community for simple step-by-step instructions on how to connect Square to WooCommerce.
To review an in-depth integration guide, please visit the WooCommerce Square Doc.