If you see your selected payment methods displaying as a red text in the multiple select box, it is because this payment method is not available.
It is likely that you have other WooCommerce settings that influence the status of this payment method, which makes it disabled.
Please head over to WooCommerce settings > Payments > All payment methods to check if you have those payment methods disabled. Chances are if you've disabled it as shown in the screenshot below, it can not be used in YayCurrency checkout permissions.
Please switch it on if you wish to use that payment method.
Otherwise, please feel free to remove the red selected payment method in YayCurrency's Checkout Options.
2. Issue with cache plugins causing selected currency to auto revert to default currency.
YayCurrency is compatible with two cache plugins currently; WP Rocket and Litespeed Cache. For other yet-to-be-supported cache plugins, you can use either of these options to exclude multicurrency from being cached:
Exclude pages relevant to multi-currency plugins from being cached, like the Shop page, Single Product Page etc. (only selected pages would not be cached).
Our cookie is; yay_currency_widget, you can exclude it in cache plugins (all pages relevant to multicurrency would not be cached).