If using Role Based Methods plugin…

At first, when I installed and enabled the WooCommerce Stripe Payment Gateway I kept getting this error on Checkout:
“Sorry, it seems that there are no available payment methods for your state. Please contact us if you require assistance or wish to make alternate arrangements.”

After much hair-pulling I discovered that my problem was that I had forgotten that my site was also using the WooCommerce Role Based Methods plugin which can set which roles can use what Shipping and Payment methods. By default, the newly installed Stripe payment gateway had no roles assigned to it — so no one could see that payment method on Checkout until I resolved that.

Hope this helps someone else keep more of their hair!