I disabled everything on the site (plugins, Pro 3.04) and the Square payment gateway works with Twenty Nineteen + WooCommerce-Square/2.0.5 (WooCommerce/3.7.1; WordPress/5.2.4)
I turn on X-Pro only, and the checkout does not work.
An error occurred, please try again or try an alternate form of payment.
Payment nonce is missing
Alternative payments give the same error. Pro 3.04 is conflicting with Woocommerce.