Why does my custom payment method is not showing in on the frontend checkout screen?

I have a problem with my payment module, which is not showing in checkout page.
Module is enabled in admin panel.
In XHR payment-information request during checkout it is returned properly, it is also returned by Magento\Payment\Model\MethodList::getAvailableMethods() method.

I don’t have any idea how to debug it deeper.

Anyone can help me?
Thank You in advance.

See How is the available payment methods list gathered for the frontend checkout page?
For example, you can set up breakpoints in the gathering process.