Is the "Your order" form covered by a gray square?

Question

WooCommerce

Hello. I must say right away that this is my first experience of communicating with woocommerce, but I have been racking my brains for the second day and just can’t figure out what’s wrong.
After you add the product to the cart, and proceed to its design, there is a column "Your order" on the right, while filling in the fields it sometimes becomes active, but literally in a moment it again becomes covered with a gray rectangle (like not available). I googled a lot, at first I solved the issue with delivery, then with payment, but the block never became "free". That is, the buttons under are not available at all, even the text does not copy.
Here's what it looks like:
blockUI blockOverlay

If you forcibly remove this overlay and hit the submit button, it throws an error in the ajax window "SyntaxError: Unexpected token <
Help please... There are no warnings in the console (browser), everything works out with a bang.
ps - php I don't know!