woocommerce setting not load

Dear Mr/Ms
I create a custom plugin payment woocommerce for my site. I read some code on web site guide, and it has image with “checkout” with woocommerce setting for example code. But it my admin woocommerce not has ‘checkout’ that is ‘payment’. When I active my plugin, the woocommerce setting page not load and invoice error.
What could I do? I don’t know what’s wrong, I check code with WP-debug already and not has anything error.

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